Many legit users have a license applied to their Microsoft account that predates the current situation. That is to say, a license carried over from windows 10 and possibly as far back as windows 7, since there was a time where Microsoft was offering free license transfers. Many people see windows 7 as being not shitty and abusive.
> there was a time where Microsoft was offering free license transfers
I don't think they ever stopped. Maybe they ceased advertising it, but installing Windows 10 over 7 or 8 would silently inherit the license far past the original terms. The time-limited offer was just a FOMO-inducing marketing scam.