You obviously predate me but, yes, I remember all that bread, and sugar sandwiches were a kind of guilty treat. But I can't remember much obesity, and certainly not amongst children (this was 60s). I'm from a poor area, and we were weighed to make sure we weren't too skinny.
I disagree with you about tomato soup, and other savoury foods being known to have a high sugar content. I certainly didn't know, and I've always thought of myself as pretty clued up. I've always been more concerned with calorie content, though, not sugar per se.
I'm not sure what the answer is. People have to eat. Carbs are easy, and cheap.