I've seen one legitimate reason to use Linux, and that was because a lot of software work on Windows is a pain in the ass. Considering how few people that applies to, I've yet to see a real reason from normal users.
Why does every reason have to be a "real" reason? Are people not allowed to simply have preferences?
Granted that obviously more programs are available to run on Windows, but there are people who believe that the ability to easily customize your system to the fullest extent, the flexibility and lightweightness, and the god-tier package management / installation outweighs this and some other facts, and in fact, do not mind using linux at all, and in some cases, prefer it completely over Windows.
Please get off your high horse and realize that just because it's not viable for you, that doesn't mean it's not viable for anybody.