It's not stupid because it's old. It's stupid and we only follow it because it's old. Were it not a tradition, we wouldn't be doing it because it doesn't make a lick of sense. Why does everyone need to have the one day they set aside to relax be on the same day? We fucking don't.
Now, if it seems I'm overreacting, it's probably because we basically have given up on it here in the US. Sure, some things close and there are still archaeic little idiocies flitting about (I can't buy beer before 5 on a Sunday... why?), but in the US we've largely gotten over it. It's horrible in the UK. While I was there, I was living in a relatively small city, with no car or bicycle. It quickly became a problem that, even in the town's major business district, on Sundays the shops all were open from something ridiculous like 12-4PM, if they were open at all (most weren't). (IIRC, pubs remained open to the late hour of 10PM... but those Euros are bigger alcoholics than us Yanks, yeah.) So, effectively, it became impossible to get food on a Sunday unless you wanted overpriced bar food or happened to be able to make it to the store in those 4 hours.
Let's not even go into the public transit (which I needed to get to campus, and I regularly needed to get to campus on Sundays to do homework).
I've experienced living in a place that does shut everything down on Sunday and lets just about everyone have that one stupid day off. The benefit of the day off is utterly crushed by your inability to do much with it. It is moronic, inefficient, and has no real reason to be implimented. Quit bitching about working Sundays, you'll get your fucking day off sooner or later.