As the other person above, this is similarity bias affecting your judgement. Which is fine, it happens, but it puts you in the wrong once you let it cloud your opinion on what happens (quote) "for most people". Most people have a legal windows 7/8/8.1/10 key that came with their computer and let them run win10.

A license for Windows 10 costs 100 bucks on Newegg. Who are these people building custom desktop computers who cannot afford $100? Custom PCs tend to be the domain of people building expensive gaming machines.

Disclosure: Microsoft employee