Why would I use Linux on Windows when I can just use Linux?

I switched from Windows 10 to Debian a year ago (didn't even bother with windows 11 with how much anti-consumer features it had).

Everything works for me on Debian, with the additional bonus that my operating system is no longer spying on me.

There's the security aspect. Windows makes you enter your product key to verify it's a legit copy. There's no such mechanism in Debian. How do you know your Debian install isn't pirated?