I decided to take a very non-representative sample, and found that in many (but not all) parts of northern California, locations of the chain tire shop that I use are closed on Sundays, but most locations in the LA area are open 7 days a week. This chain has a lot of locations. It could be that they're responding to what their competitors do in both cases. So maybe getting tires on Sunday is a so-cal thing? TBH, I personally am more used to expecting the tire shop to be open 7 days a week, unless it was a small, locally-owned place.