It is another of those 'we can do it so we will do it' things.
Shops already get 96 hours opening every week, that's almost 60% of the time, how much more do they NEED?
Opening whenever they can, because, is not much of a moot point if you are one of the poor sods covering shifts 24/7. Where one week your 'weekend' is Tuesday and Thursday and the next it is Friday and Monday and also with your shifts all over the place.
It is noticeable that some supermarkets have stopped doing 24hr opening in some places because there is no call for it.