It's even simpler then that.
It's which games use EAC or BattleEYE and have dog shit devs that won't just turn on proton support. It's seriously just this at this point. I feel like every time I go looking though protonDB a majority of the garbage rated games are anticheat/drm related problems.
Fucking fromsoft games use EAC and they have worked out of the box day 1 on Linux.
CVS near me gives you a store credit if you let them email your receipt to you. It's silly.