It's only for the convenience and visibility, nothing more, nothing less :)
This way, if someone is not interested in checking threads that are tagged, they can skip it after a short glance.

Makes me very happy that you like the idea!

PS. I tagged those threads that I've found so it's possible that there are still some active ones that are not tagged. Feel free to send me a link in such cases.

Giveaways are not actual "games" in my humble opinion.
Nor are "What made you happy" or "Post a screenshot" - those are made for sharing and some posts can even start a short discussion ;)