Yes, I concede these niche operating systems won't show me ads. But can I play an HDR YouTube video in a web browser on my HDR display using FreeBSD or OpenBSD? No. One can't even do this with Linux yet as far as I know, though Firefox on Linux recently in the past few months now has experimental HDR support (haven't tried it yet).
Sure, but that's a fair bit of extra time and friction to watch an HDR video versus just clicking the play button on Windows or Mac and being done with it. It's also nice on Windows how every Steam game launches and runs without a "missing libfoo.so" error like you get for a number of games on Linux, though I'm glad Linux support continues to improve and look forward to switching back to Linux from Windows when there are sufficiently few issues I have to research how to work around and fix.