Interest in these kind of decentralized behavioral patterns is rising, which could revolutionize our views on the utility of traditions such as the 'day of rest'.
The UK retail landscape has changed dramatically since then and in unanticipated ways. Newsagents ceased to be the cornerstone of community that they once were, nowadays we have convenience stores where most people don't walk out with a newspaper under their arm.
Maggie Thatcher was the one that pushed for the Sunday trading laws to be changed, thereafter we became a nation of shoppers (rather than shopkeepers, which was how we described Britain before then). I did not shop on Sunday for many years after that as I did not see the point of having sales spread out over 7 days. Also remember that we also had half day trading on Wednesdays (or another mid-week day) in most towns. So this was a big change.
I think that we would do well to re-visit Sunday trading with more 'Bank Holidays' on Sundays. The weekend after pay day might be good for Sunday trading with the rest of the Sundays being retail free days. We could also do with a few 'car free' Sundays combined with wither no retail or lots of retail more of the 'street festival' flavour.
In the days when the shops were closed on Sundays nobody starved.
My feelings about Sunday are like those of many Americans over Christmas or Thanksgiving. You don't interrupt people and you can't judge people for being unavailable. Most Americans have a cultural appreciation of how those days affect life even if they don't personally celebrate.
I should note I'm not really disagreeing with you - I think people should be able to do what they want - but I wanted to reflect on the idea there are cultural pros and cons in all directions and that restrictions can have a point (and beneficial side effects) even if that point must expire someday.
The only argument I can see for it is that it allows retail workers a day off when they would otherwise not have the power to demand one.
But, well, locations and families vary. I've lived here over 30 years and Sunday has a distinctly restful vibe for most groups of people I know. I imagine people down in the Home Counties are more rush-rush-busy-busy nowadays than we country folk.
Even as a non-believer I like these rules and even miss the older ones. Having Sunday be a generally accepted "day of rest" (even if you don't observe it yourself) appeals to me as a way of having a shared cultural "rhythm" to life. Germany's "quiet time" laws seem to play a similar role there. I appreciate not everyone likes such cultural harmonization (or restrictions, based on your POV), however, and things are likely to liberalize further nonetheless.