I used to work in retail. As a lone parent. I started in a job that was mon-fri 9.30-5.30. Which fitted in PERFECTLY with nursery/ kids club pick up times. The company got taken over, and INSISTED that we all had to work one weekend day. Because the bastard manager was 'getting rid of' the student who wroked weekends. I was then basically told 'suck it up and do the shifts, or you'll be out of (your crappy minimum wage) job, I need staff that will work the hours I want. I had no family, and no-one that would look after a non-mobile 2yo, a 3.5yo AND an asd 7.5yo (as my dc's were at the time). I just couldn't do it, so lost my job. Because the government paid to train me in my old trade, I can't get funding to retrain. Because of my dx of epilepsy, I can no longer EVER work in my previous field due to legal restrictions. So no I can't F'ing re-train. I do shit retail work for shit wages to get treated like shit, or didn't work.
I managed perfectly well doing my shopping at all the other times of the day and night when working full time, and still fitted in time to spend with my DC's, have never felt the need to shop on a sunday, what could possibly be that important that it can't wait until monday?.
You don't actually have to GO to the shops on a sunday, even if they are open. I am just opposed to this because of the extra stresses it places on a lot of their staff.
OP, YABU, not everyone in retail gets a choice whether or not to work Sundays, whether it's practical for them or not. Often you can't GET a retail job without agreeing to work at least a minimum of one sunday in 4 even if you have absolutely NO childcare at the weekends. WTF do LP's without family support DO with their DC's if they have to work on a Sunday??