I don't know how old you are, but in my experience of growing up at that time there was a huge amount of processed food eaten back then, and it was being heavily pushed in supermarkets and in adverts. Spaghetti hoops, Findus crispy pancakes, Angel Delight, Instant Whip, frozen pizzas, Nimble bread, Vesta curries - I could go on. I have no idea what the food labelling regulations were, but even if the ingredients were listed most people didn't look at them, or not in the circles where I grew up.
As women started to work more outside the home and electrical equipment like freezers and microwaves became affordable and widely used it was a huge boon to have convenience foods. It was also considered the modern, scientific way.
When a few lone voices started trying to point out back then that there were all sorts of problems with eating this highly-processed, not very nutritious food, they were pooh poohed as killjoys, not living in the real world, old-fashioned, doom-mongers, and so on and so forth. And here we are now, with huge multinational conglomerates keen to protect their extremely profitable business models, rising obesity problems across all the rich countries, and abysmal knowledge about food, cooking and nutrition embedded across the UK.
We didn't get here just in the last few years.