We sometimes have to do our weekly shop on a Sunday; doing it during the 'middle' of the day suits us and many others I know.
So once again this is a case of people being expected to fit their lives around the shop opening times.
The problem with the 10-4 or 11-5 position is that it takes out the middle of the day. So if you want to do something else, e.g. as a family - you can't. If you can get in at 8am (just as you can on any other day) or perhaps at 7pm (just as you can on any other day) you can fit your shopping around your life, not the other way around.
So it might suit you (and therefore change or no change has no effect) but really rather ofter it doesn't suit met and my family. Your attitude seems to be a bit 'I'm all right Jack, don't give a stuff about you'. But I'm also prepared to bet that you, like me, have sometimes been doing a DIY job, or perhaps some bike repair, or maybe working in the garden. Suddenly realised you need something rather vital to complete the job on a Sunday afternoon and discovered to your horror that it is 3:55 and the relevant shop will be forced to close (although they probably don't want to) in five minutes time.
But the larger point is this. If shops want to open as long on a Sunday as they do on other days and there are people happy to work those times (which already happens in all sorts of other places) and there are people who want to shop at those time, why on earth are they prevented from doing so.
So look at my upcoming weekend - and I haven't even thrown in 3 kids parties that the kids will need to be ferried to. Saturday is completely out, as is the whole of Sunday afternoon. And my daughter has a party on Sunday morning from 11. So if she needs new shoes (for example), explain to me when exactly we are going do that? If the shoe shop was open from 9 on Sunday (as they are on every other day) then all if fine. But they aren't - they don't open until 11.