Do you have any other applications installed that could possibly be fighting with Illustrator for association with EPS files. I've seen CorelDRAW do it before. Several other graphics applications can open/import EPS files (with varying degrees of success/failure).
This is true, it appears that it's the windows update that changes the default programs from time to time (not the first time this has happened with these type of programs, but even with MS' own branded programs as well (which I'm not surprised of).
I have to wonder if the update did other things as well. Getting the File Explorer, instead of having the easy option of being able to point to programs that the OS recognizes as being able to read the file makes me wonder. I also have to wonder, the attached is with an EPS file and Acrobat (even though I have pro installed) wasn't apart of the recommended list. Now that could be a function of being CS6 and maybe that changed with how CC recognizes things and relays that to the OS, I dunno.
sorry still on windows 7 back here refuse to go to 10. makes you wonder WHY they fixed it so you cannot turn off updates doesnt it
Double edge sword.
I know you don't believe that the OS needs patches, bug fixes etc, but in all honesty those things are needed, especially with Windows. Windows has a lot of legacy code in it, some of which was buggy for a very long time. Back in 2015, 2016 when Win 10 was still "young", there was a printing protocol that could have been exploited (zero day) that had existed in Windows since Win 95. That's a long time that the code had been in there and not changed, at least with regard to that zero day.
Personally, I wouldn't have a problem so much with forced bug fixes/patches and things along those lines, but when one has forced feature upgrades/removals that's something else. Updates have the double edge of fixing things (hopefully), but also running the chance of breaking things (why as a whole people try to delay that pain as much as possible) and that's on a good day. Image what it is like when features are added or removed as well in major updates?
Keep in mind too, there is also fragmentation within the Windows hardware ecosystem, a lot of combinations of hardware/software. MS can't account for all of that, so after Windows does it's thing, then have to wait for 3rd party OEMs to do their thing.