I think that there is less of a respect for personal space in the UK. I've noticed this outside as well as in shops, and like phatbeetle, I think I have gotten used to it and become one of the shovers back.
I used to get annoyed when I would be looking for something on the shelf and people would just reach their hands in front of me to grab what they wanted instead of waiting for me to finish.
But then I've noticed that people will stand in front of the shelf chatting while I'm patiently waiting to reach something so I just say "Excuse me" and stick my hand in. At least I say "Excuse me".
It is like people have no idea that there are other people who also want to get their shopping done.
NoseOverTail, I have had the same experience as you in UK supermarkets but never in the US (New York City) - where you back out of the way to let someone pass and they just stand their like deer in headlights.
Sometimes there will be one person coming in one direction and two people in the opposite direction, and it is impossible for anyone to move unless someone backs up, and nobody but me can figure that out.
I usually have to say “Go ahead” and signal with my hands to get them to figure out what needs to be done or we will be there all day and all night.
But in the supermarket there are no lanes or speed limits.
You should not need lanes or speed limits to do this.
I used to work in Manhattan where the pavements were packed with people rushing to get wherever they wanted to go. Everybody managed to get through the crowds without delaying other people or causing injuries.
I don’t have a driving license and yet I can figure out what I need to do to make sure that I am not in someone else’s way and they not are in mine.
Regarding reading labels, people read labels because they want to know what is in the food they are eating. The information on the internet is not always accurate. Some people are on diets. Some people have food allergies and if there is the tiniest amount of the wrong substance the food will kill them. Some people want to check how they can store an item or how long they can keep it before it goes bad. Some people want to see if the ingredients in the item are worth what they are paying for it.
You can read a label quickly without getting in other people’s way.