I'm sure half the reason for this is that most newer games are all changing requirements as well. Its been planned for quite some time, at least for Windows 7, I was unaware it would be on 8/8.1 as well...which makes my statement more likely to be right.
I know there are workarounds and such (also agree its BS ftr), but on the developer end so much as implementing new sound features added to Windows 10 as well as all the graphics enhancements and still making them work for Windows 7 is a serious chore.
My theory on it from a dev aspect personally is if it works, don't fix it...especially if it works for older operating systems, if the games is old enough to have been coded for Windows 7 then most sales will likely come from that OS now anyways or there won't be enough to justify overhauling it to add newer features and screwing over people who bought it for Windows 7.
But thats my view, people are idiots and will try to scrape every dollar out of a few more sales rather than be loyal to their customers unfortunately.
I was one of the die hard Windows 7 users, even as a dev...but eventually when trying to reinstall onto bigger drives I had to use GPT and I couldn't copy my file properly anyways so rather than deal with fighting a dying OS I just upgraded my gaming drives to Win 10.
My programming drive however hasn't used an internet connection in ages and remains Windows 7 (even with my login screen at 1080p on 4K

) and I refuse to upgrade it so I can continue to make programs that work for Windows 7 as well as the new versions.
Once I can afford to upgrade my motherboard I intend to keep the old one and the programming drive in a second rig and start another programming drive for my main rig since I won't be able to use Windows 7 on a newer chipset--the main reason I never upgraded it before.