I doubt that's the reason, otherwise you'd see a huge boost when 8 was released.

It's constantly growing

Windows 8 wasn't forced down people's throat.

Neither is 10, and 8 was an absolute disaster in comparison.

I actually liked windows 8 more than windows 7 but that's just my opinion.

Booted my computer, was greeted with the windows 10 installation process...
(I had to deny the TOS in order to stop it)

w8 wasn't free for a year like w10 was.

Yeah, it kinda was.

When specific applications need to be created to block updates and nag notifications on Windows 7, that's pretty sad.

And most gamers didn't give a shit about Windows 8 because it provided absolutely no performance or quality improvements beyond 7, so it was a non-issue.