Riven Why don't you think children should sit in the trolley. My children don't arse around - they sit in the trolley. Trolley's have high sides - they don't need straps for safety.
Yes it is more difficult to take a trolley and a buggy in, to say otherwise is daft. It also clutters up a busy supermarket even more (and yes, I do understand you need both for your DD and that's fine) we don't need every parent using both in the supermarket, we'd never get moved in there!).
Define sensible - I think it's sensible to put little ones in the trolley because they get knocked by baskets and other peoples trolly's when they are small and are walking around the shop. Admittedly I prefer them in the front seat, but if they didn't fit or would be much happier in the big bit, then they would go in the big bit.
A buggy is not a toy, a high chair is not a toy - they sit in those? Your point is?
I know your older ones are teenagers and there wasn't the internet option like there is now. People shopped more locally, more often. Lots of things are done differently - life moves on.
If your DD was NT and you drove to the supermarket and she was tired/whingey and you just wanted to get the shopping done, keep her in a good mood and not be worrying about her getting knocked by someone elses trolley or basket (which does happen even when they are standing right next to you) - how absolutely sure are you that you wouldn't put her in the trolley??
It is not part of the culture of not saying 'No' - mind understand the concept of 'No' just fine. I am a strict parent, not a 'let them do as they please' parent by any stretch of the imaginiation.
It's got nothing to do with them walking 'nicely' either. I am not getting them knocked by other people not looking where they are going and this does happen, no matter how 'nicely' they walk or how close to the trolley.
Putting a child in the trolley has nothing to do with sitting nicely in a restaurant, which mine are also very good at.