Because kernel level anti-cheat can be circumvented by modifying the kernel which Linux allows. -Kudos to the devs for not allowing cheaters. Also, these games have ‘minimum spec’ requirements where Linux is nowhere to be found on those specs. -They don’t owe Linux users their support. And as you say ‘Very often’ - which implies there are still great games that simply don’t work.

Dual booting is a bother, and an overhead on storage as well as a main tech support issue for Linux users. Gaming in Linux isn’t so straight forward either.