Linux usability has come a long way in recent years. I switched full time to Linux in 2006, but I can absolutely understand those who wouldn't back then.

These days? Unless there is a specific piece of software that can't run on Linux (or under Wine), and there is no suitable replacement for it? Yeah I don't know why you would voluntarily stay on Windows (note voluntarily, if IT policy says you must that doesn't count).

Accessibility.

All accessibility stacks sucks in some respect, but Linux's sucks most of all, and Wayland people in particular don't seem to be willing to compromise on security (which is required for accessibility to work).