I think that there are multiple things at play:

1. The statistics only show Desktop usage relative to each other. But I could totally imagine that macOS "loses" users to iPadOS. Similarly, Windows could be losing users to smartphones in general (I see more and more people who don't actually have a personal computer anymore).

2. Valve (and others, surely) is doing an incredible job with video games on Linux. 20 years ago, I needed a dual boot just to play games. I dropped Windows when I stopped playing, and I started playing again thanks to the Steam Deck. I am convinced that many people today "need" an OS on which they can play video games, except that today they have a choice (thanks to Valve and others).

3. Privacy. I think it's becoming a lot more important outside the US (it's actually now a national security concern there), but I'm convinced that people are slowly learning about that. TooBigTech pushing to train their AIs with everything the users do surely has an impact on that.

> Similarly, Windows could be losing users to smartphones in general

But this is desktop only. If someone stop using windows completely, it won't show a decrease in windows usage. This will basically only show when people switch from desktop OS.