Partly because newly released games are buggy and unfinished and they can take a while before they're stable and quality of life features fully in place.
I don't want to pay to be a beta tester, and I especially don't want to pay full price for that. I can wait a bit and get a better game for cheaper.
I've only bought a couple of games on early release or at release lately. Deep Rock Galactic Survivor because it had a demo I enjoyed, and Hades 2 because I trust that studio and Hades is one of my favourite games.

I'd do the same...