Especially because devs actually have to go out of their way to exclude Linux these days. Proton makes it so damn easy to support Linux. If you don't, it's because you did not even try or you intentionally added some bloat to your software to make it incompatible.
At this point, windows-only title that won't work on Linux are overpriced cash grab with multiple layers of intrusive DRM that will try to wring you out for more money for a year before dropping the still unfinished thing off the support line.
The reason I started playing on PC is because I want the best experience for each game, and ability to play most of them. If I have to ignore certain games that don't support Linux, I lose that.
Mad respect to those of you that prioritize software freedom and Linux support, but that's not me.
I remember playing RE: Village and FF VII Remake on Linux after quitting Windows for good and thinking: "Holy shit, this stuff really works, even with recent games with high end graphics!"
If I can't get it working on Linux I get a refund. For the past two years my Steam year in reviews have showed 100% of my play time was on either Steam Deck or desktop Linux.
In the age of the Steam Deck and Proton, the Windows API has largely been demoted to a virtual machine that is already implemented on Linux. Given that some 5% of the market play on Linux, game publishers have an incentive to not write their Windows code in such a way that it breaks on Proton.
That's what I'm doing nowadays.
Except for Sniper Elite (version 1), which I paid for on Steam, because I felt like I owed something.
Thinking about it now, I should have bought the GoG version.
Jerry: Well ... you want something to play, don't you?
Kramer: Ahh, no, no, no. You got me all wrong buddy. I am loving this no Windows Gaming. You know what I discovered? I really like depriving myself of things. It's fun. Very monastic.