Because I don't think, new "Sticky-Threads" are really noticed by most.

Apparently, GOG can now generate "special promo codes", which we will be able to insert in a newly included mask at the checkout window, to get better (lower) prices.

The old codes, provided via newsletters, will allegedly stay the way they are - nothing will change about them.

https://www.gog.com/forum/general/new_checkout_functionality_is_releasing_today

why is GOG spiralling down? (what does it mean?) and how to reverse or fix this or is it bad or good?

Hmm... random thought out of nowhere. This promo code thing and GOG' increasing ties with Amazon through Luna, is there a possible acquisition deal slowly developing in the background?