My reasoning is that Vulkan has not been out quite long enough for a more widespread adoption, especially as dev cycles take years, as I'm sure you know. Whereas in a few years, there will be no excuse for game devs.
There will always be excuses. Right now unity should make it very easy to make multiplatform releases, yet so many unity games are released for windows only. With or without excuses, the excuses are bullcrap.
That said, I am, I agree, and applaud your "speaking with your wallet."
It's really nice to stand behind one's principles when making purchasing decisions. But let's not pretend speaking/voting with one's wallet really matters unless a majority of the target audience make that vote. Just like in democracy, the minority that keeps voting for their 2% party will forever be subject to the tyranny of the majority :(
The linux users who choose not to purchase a game for its lack of native platform support are but a few among the 7.6 billion people on planet earth who chose not to purchase said game for whatever reason. The devs & publishers won't ever know or care, unless people repeatedly make a loud vocal shitstorm about it (and even then most of them just don't care).
Perhaps there will always be BS excuses, but again, after Vulkan has been out awhile longer, I'm done; I'm of the opinion that at that time there are no more valid excuses and as such will not support Windows only games.
This isn't politics, it's business. Regardless of minority (and to what extent, who knows?), Linux sales lost are sales lost, and when it's dead simple to port to Linux, devs are stupid to leave money on the table. They've largely woken up to that fact re: PC gaming, and I believe they will realize it re: Linux in time as well. If not, there's plenty to play.
I will never be among the sheep, without control of my computer, being fed adverts while my data is mined, on a locked down, unstable, cobbled together, bloated system built by the soulless lying incompetents and malware peddlers that make up M$. It's a matter of principle.
Change needs to start somewhere. If that's a vocal minority complaining about unsupported games and refusing to buy them, I'm quite content to be among that minority. And I do think it's important and fully intend to be vocal directly to developers as well, praising their inclusion of Linux as a deciding factor in buying, or in not buying in the case of them not having Linux support.