I switched because I was called out, because I was google-shaming android users for the lulz. Didn't regret it.
As a HDD user, Linux boots way faster than Windows. Windows used to boot for 4-5 minutes (measured it after defragging). Linux boots at 1 minute, with an encrypted HDD (including system).
As >>13031 said, it is customizable. If you don't like how it looks, you can switch DEs, and in some DEs you can change even certain components. (DE = desktop environment, the graphical interface)
To put something new to this, scriptability is also nice. Things like cronjobs make automation on Linux pretty easy. And you don't even have to know a programming language for automation. You can write your scripts in bash, which means, you can literally just enter the name (or path) of the program you want to execute at time x, with all the args.
Superior installation process for most of the programs, no annoying system updates (they take about a minute or so), don't have to reboot for system updates, no forced updates, as the guy above mentioned no tracking, don't need a user account to use.
That being said, I can understand why people who use their computers for games might want windows. I don't know the state of Linux gaming, never installed wine. Dual booted for a month before full on switching, but never turned back. I use my computer for work (writing), the average joe stuff, with some scripting as a hobby.