Yes, it should be up to individuals. I think we are seeing a shift to companies being open and Saturdays and closing on Mondays. Saturday is day for people to shop, so it seemed practical. Sundays are a good day to shop too, so I foresee maybe being closed on Mondays and Tuesdays or something like that.
A lot of stuff closes Monday here now as well...
I find it intensely annoying as Monday is my husband's only day off.