Using XP on my Laptop as max ram is 160mb and nothing else will work apart from 98. Most of the Win 10 updates are rolled up in a cumulative update, but if you look at the win 10 history site there is a lot of bug fixes in there and some security fixes too.
I had a few for Windows 8.1 as well, one of them I have no idea what it does, if I cick on the link to find out what it does I get a error on the website saying it can not be found, so until I find out what it does, it will stay hidden.
Desktop machine now powered by windows 8.1 pro 64bit, no dreaded metro, laptop by Linux
Or it could be that W7 is a good OS and needs very few updates/fixes.
Much of the code base has remained unchanged since Vista, which is why when updates are released very often there will be updates for the same issue for Vista, 7, 8.1 and 10 simultaneously, e.g this one released a few days ago https://support.microsoft.com/en-us/kb/3148527