The default Microsoft file locations are a really terrible place to store stuff. At least in Win 7 they are not accessible without repeatedly jumping through hoops. You have to not only have admin access, but need to change the permissions at every file level and not at the intuitive location. You don't have permission to change the permissions using the normal interface and have to go two screens deeper and since they're not inherited you have to do so at every folder level.
Save files cannot be migrated, modding and installing non-multiverse mods is impossible, and the settings cannot be changed.
It's possible security became less stupid in 8 or 10, but it should be possible to change game settings, migrate saves, and use mods without admin access.