Back in the late 1970's and early 80's when I worked part-time in retail, Massachusetts had "Blue Laws" in effect which prohibited all stores, except drug stores and convenience stores, from being open on Sundays. They eventually allowed almost everything to be open on the Sundays between Thanksgiving and Christmas, then that went to year-round a few years later.
One Blue Law that is still in effect here is that retail stores cannot be open on Thanksgiving. So everything will open up at 12:01 AM on Friday. I believe studies have shown that stores never got any extra money by opening earlier and earlier, just the same business spread out over a longer time.
But .... since Store A is open early, Store B must be open to 'compete' and not loose any business to Store A. Unfortunately, enough crazy people keep going to these early openings (with full TV coverage) so I don't see an end to the practice anytime soon.