This is how I was brought up
We only ate in the home, breakfast lunch and dinner - or dinner/ tea, Puddings were for Sundays, sweets and biscuits were rationed - dolled out by parents, none of this helping yourself.
There weren't 24 hr food outlets. Take away was fish and chips, Chinese or a KFC which would be bought for a family meal to be eaten at home. I can remember when Mc'Ds came, we got dressed up and it was "a meal out" :) Certainly no eating in the street, the only time you ate in the street was on a day trip to the seaside and you sat on a wall to eat your fish and chips
I went wrong when I moved in by myself. I worked for the NHS and had access to a cheap dinner every day, but I have never liked mass catering, couldn't abide school dinners and works canteen was so similar. So Id grab a sandwich then coming in from work, stomach feeling like the throat had been cut, it was easy to pop in the nearest FF take out, of which come the 80's were everywhere. And I got the taste of fat laden, highly salted, highly processed food and being a single woman living alone it was soooooo easy
Joke is Im a very good cook, Ive worked in professional kitchens a lot of my life ( no chef, learned on the job ) but the thought of shopping, prepping and cooking was just too much, take out was so easy and tasty
Now thankfully the tide has turned, processed food upsets my stomach, from being awake all night dying of thirst to all out stomach cramps and nuclear fall out. Even white bread bloats me so much and makes me so obviously "liverish" as we used to say, within minutes, I do have to weigh up how much discomfort Im willing to put up with :)
But now Im back on a mostly home cooked diet , just meals, keeping the snacks to treats, im maintaining a steady weight. Your Gran weren't far wrong