Going so far as into the 80s the pork belly was bought and sold as a kitchen “swiss army knife” of sorts.
It was to eat, sure. But everyone knew it was the junk cut of meat. The pork tenderloin was what people were supposed to eat.
But yeah, we had the bucket of manteca on the farm. It was how we cooked. took way too much butter to for it to be effective in a lot of applications, but pork belly produced tons of fat that could be used to all purposes. Hell, I moisturized my car door rubber seals with it when I was a kid. We used to grease the hose before putting it away for the winter. We used lard for tons of things.