I agree that for you it doesn't make sense, but outside of the "competitive" FPS genre compatibility covers most everything else, minus things with crazy kernel level DRM rootkits. But you really shouldn't be playing those on Windows either IMHO. And if more people didn't support them on Windows devs might be forced to use compatible anti-cheat that would benefit gamers on all platforms.
I'm also a casual gamer that will just move onto something else in my backlog if a dev breaks proton compatibility.
I think the point is that they outnumber us by many billions, but humans see themselves as ruling the earth because of our size.