A lot of people would be happy to leave Windows behind. Gaming performance, simplicity of setup, and other Linux obstacles have held many people back thus far. But the gap has been closing for a long time now and Linux does tend to seem more viable than ever. For a lot of people that few percent difference in performance numbers or little user friendly details hold people back. It's probably at the point where if I actually put the effort into Linux I'd find I kind of hate enough stuff about Windows to make the switch.
Gaming performance? You like your games running slower in Windows? xD
Just look at the plenty comparisons between the Steam deck and the Ally when running the same games and their 1% lows. Even at 15W mode, it beats in many titles the Ally at >30W. Bananas. Proton is at a point where it's just amazing. One asterisk and the one I alluded to, is the driver maturity and its surrounding tools. That I can accept it's behind, but not as far as it was a while ago.
Simplicity of setup... I don't know what you mean there, but installing Linux nowadays (Ubuntu, Suse, Debian, Mint and SteamOS) are super easy and with a lot of help already built in and no BS. Well, a little bit, but acceptable. Each distro does it slightly differently, but I'd be moving into either Mint or SeamOS.
As a daily use OS, and this is using the Steam Deck as a normal PC with the "desktop mode", I just see nothing that is harder or more complicated for the average user. Different, sure, but not harder or more intrincate. In fact, I find some usability things (they bundle KDE with SteamOS) are really good and coherent, unlike in Windows. Hell, I'd even say the UI is WAY more polished in KDE Plasma than Windows 10/11.
Regards.