There are still some people who run 7 because they don't want to move to 10. Windows 8 is a little bit like Vista, where it's skipped because people either kept on XP or moved to 7 as soon as they could.Just curious, but why no support for Windows 8.1, but there is for 7?!
I recall early in Windows 10's release where XP still had more people using it than Windows 8, so it's not surprising that it doesn't get support. It's already outdated, but it doesn't have a massive amount of users like Windows 7.
I did some more digging for updated stats and it seems that this is still the case. One site that tracks marketshare for the different versions of Windows has stats for 2019:
Windows 10: 52%
Windows 7: 36%
Windows 8.1: 7%
Funny enough, XP has more share than 8. I'm kind of floored that people are still running an OS that's over 15 years old at this point.