vista was killed by first impressions. Wrapping it in a new cover was enough to convince people that this "new windows" was better than vista, they learned that with an experiment they ran a few years into vista. Win 7 isn't exactly win vista with a face lift, they did change the kernel a little as it needs less ram to run than Vista did. Win 10 beats them all when it comes to what minimum ram it will boot with. Only XP beats it and that is cause average ram total for PC 20 years ago wasn't very big.
Peoples love for 7 is similar to all those that loved XP before, change is bad... it worked perfectly fine in the past, why change? The technology that Windows runs on has changed in 20 years, as has windows itself, so until win 10 was released, if Microsoft wanted to change something big, they would likely make a new versions around changes, or release a Service Pack. With Win 10 they just add it to a version update and everyone with win 10 gets it free.
on topic: you only get an update once per month, is that really too much to ask for added security and potentially less bugs. 95% of programs that run on 7 run on 10, the only reason to run 7 now is if the software you use needs XP compatibility, and if thats case, you need new software soon.