However:
1) The economy sucks right now and even game sales have felt the hit. Selling old games at a discount would at least get them some money, if the new games at full price already aren't selling as well as expected.
2) Ummmm... actually there is no 2, 1 pretty much covered the only point I wanted to make.

As mentioned, selling older games isn't guaranteed to turn a great profit. So that rules out retail, entirely.
So that leaves us with digital distribution, which is designed around selling niche items. The problem there is that the contracts/licenses may treat it as a grey area (I know that was a complaint with showing TV online), and it pisses off the retailers.
Yup, the retail chains hate digital distribution. It is threatening to wipe them out (if you want a box, order it from Amazon. Otherwise, just buy the game and ignore Gamestop). And while I doubt those retailers expect to see ToEE on their shelves, it still is going to make them feel left out. And that can come back to bite the publisher in the butt when a major release is boycotted/given crap exposure ("Oh yeah. I think we have a copy of that in the back. Let me look" as opposed to shelves full of a game). That is the real reason behind all these store-specific preorder bonuses. It is providing incentive to get retail (beyond the box).
And, beyond that, they run into the issue of support. Even Bethesda was very wary of re-releasing Daggerfall in any form because of how buggy that game still is, and because it barely even ran in DOSBox for the longest time. Fortunately, they remembered that nobody really cares about how pisspoor their support has always been, and that we expect buggy games from them. So free Daggerfall :p
And while you might argue that a website like GoG will take care of that, that then snubs all the other sites (Steam, Impulse) who expect the publisher (who expects the dev team) to be responsible for making it work. Steam gets bad publicity because yet another Strategy First title doesn't work, Strategy First gets bad publicity because yet another Strategy First title doesn't work :p. Then you run into the problem of Steam or Impulse not wanting to carry their next major release. Because even though GoG isn't directly competing with most of the other stores, they are a major competitor for the cheap back-catalogue games that people tend to buy on impulse/on sale.

We're talking about PC games here. What major retailer out there uses more than a three-foot section of end cap to display their PC games and wouldn't be happier using it to display something like console games instead? PC gaming in retail outlets might as well not even exist anymore and is certainly not something that retailers are going to miss or fight for. Digital download services are soon to be the only way to get the full selection of available PC games and retailers are fine with that, since PC games are a dead market for them.
The question of support is an issue, but just as with those bargain bin games they do still sell in retail stores, older games should always be considered an "as is" sale. The consumer should already be aware that the game they are getting is old and most likely not supported, except by the community. As long as that is made perfectly clear at the time of sale, publishers should have absolutely no issues with selling their old games again.

Best Buy tends to have at least an aisle for PC games.
And either way, everyone had at least a few shelves of Modern Warfare 2, and almost always have a shelf of WoW. That leaves precious little for the other games (which are almost always the Valve games and Blizzard games :p) in a Gamestop.
Either way though, imagine what is going to happen when F3: New Vegas comes out. I sincerely doubt that game will generate anywhere near as much hype as MW2 did. So the only hope for impulse buyers or parents is going to be shelf space (however little of it there is). Do you really want the retailer to have an (un)official policy of "Put these games behind other ones"?
And retailers are already pissed about digital distribution. Take a look at the PSP Go. Quite a few retailers refuse to stock that, because it only supports digital distribution. Sure that was for a (handheld) console, but it sets a precedent.
Hell, Impulse and a few other sites refused to carry MW2 because of Steam. So if a bunch of fairly small digital distributors can afford to boycott the current "game of the millennium", retailers who already turn most of their profits on TVs and consoles aren't going to think twice if they get the feeling that they are being neglected.
And trust me, if BG2 or Planescape actually sells like hotcakes (ie. if people can ignore the non-3d graphics), retailers will be PISSED. Because if any older game can still sell like hotcakes in today's market, it is going to be one of those. But that is still a big "if", since graphics matter so much these days.
As for the bargain bin games: Yeah, that might work. Although, I have a sneaking suspicion that a lot of those haven't been manufactured in a few years, considering that, over the course of three years, I saw the exact same copy of Rainbow Six on the shelf of Best Buy every single time I went (the stickery thing had been torn just slightly, so I was able to identify it).
And either way, if they want to turn a profit at all on these, there is going to be advertisement. Maybe they won't bother with ToEE, but BG2? And that will effectively make it count as "new" in the eyes of the target demographic (not us).
Maybe it would work, maybe it wouldn't. But it isn't as simple as we would like it to be.

Honestly, I haven't bought a PC game in a store in years. Once Steam came on the scene, there wasn't much reason to. With all the other download services out there now, there is even less reason to. It wouldn't change a thing and matters very little to me and a lot of other PC gamers if retail stores stopped selling boxed PC games entirely. The retailers pretty much feel the same way, hence why they no longer dedicate much space to PC games in the first place. Best Buy may be an exception, but that is changing. My local store just went from an entire aisle of PC games and other software to one 12 foot section that includes all PC software, less than half of which are games (and the selection sucks at that). Most of the software they offer are things like Windows 7, Office, anti-virus products, etc. Retailers know they can make their gaming money off of consoles rather than PCs now. Sure PSP Go is an exception to that, but the PSP brand isn't a major concern for most of them when the DS and its variants are where the money is at in handhelds. They might not be happy about the advent of digital download services, but the reality is, they no longer have to dedicate store space to products that barely crawl out the door and can focus on much more profitable items. In the long run, it is better for them to stop carrying those products and they know it.

Unless someone buys the games from Atari like they did with Interplay, then it's not about to make anything any easier. In fact all this does is highlight what a bitch Hasbro is to work with.
That's a good point. I probably should look to get that expansion for it. I wonder if digital versions work with the retail version of the game.

The unpatched game also had fun bug that caused uninstallation of the game to wipe out your system fles in the process. :P They apparently did not include wizard, bard or druid classes in the game for some reason. Here's Ars Technica review of the game.
Edit: Aww crap, internet ate my post. At least it was easy to rewrite.

the real story is, Atari is going tits up if they lose. Interplay 2.0.

Atari is financially screwed up and inept, I hope they lose the license, and die off as soon as possible.

If that happens, it could make it even more difficult for GOG to get a hold of any of the IPs that Atari still owns. As much as we may dislike the path Atari has followed, as long as they still exist, GOG has a single clear entity to negotiate with. A collapse of the company could lead to years of legal wrangling, just to decide who actually owns the rights to any of their old games before GOG can even try to negotiate with the "victor".