As someone who uses Linux as their main OS, I can tell you a few:

1. Ugly UIs: Of all the distros I've tried, the only one that doesn't make me wanna gouge my eyes out is Ubuntu. Most Linux users seem to have accustomed to ugly UIs to the point that they don't notice their ugliness anymore.

2. Bad UX: I've been using Gnome shell for 2 years and I still don't understand it. I never remember if ALT+TAB switches between groups of windows or between windows, or between windows in the same group. Or was that ALT+ESC?. I've never had such issues on Windows. Am I just too stupid for Gnome?

Also, why do I have to edit 2 obscure files (from the POV of a regular user) in order to have a simple 'show desktop' button in my taskbar?

Also, why do I have to install an external application (Gnome tweak tool) to disable mouse acceleration? And if you're not on Gnome, good luck trying to use libinput (used by Linux Mint and Ubuntu Mate) directly, because for some bizarre reason the "flat acceleration profile" setting is ignored if you're using a touchpad.

Also, why do I have to install an external plugin and edit an obscure file to have audio compression/normalization when Windows has a single checkbox that reads "Enable audio normalization"

Also, why does PulseAudio start to crackle each time I open reader mode on Firefox?

* Note: You can choose a desktop environment with decent UX, but it will look ugly (xfce). Or you can choose a DE that looks good but has bad UX (Gnome Shell with Ubuntu customizations)

3. If the app you want isn't in your distro repos, you have 2 choices:

a) Install a ppa whose server doesn't work anymore, so now each time you update your repos, there'll be ugly warnings about the dead server. Now you have to Google "how to remove ppa" and choose between 5 articles telling you 5 different ways to do it.

b) download a .tar.gz and spend 1 hour installing the right dependencies the right way, and then 'make'ing and 'make install'ing only to find that there's some obscure error.

After all of this, I still use Linux because I think Windows is slightly worse overall. But would totally understand why some people still choose Windows.