In many places, Cubagirl, a whole street would keep a pig. They would feed it their scraps for the year and when it was ready it was slaughtered and shared out - pigs will eat (and thrive!) on anything, and the saying goes that the only thing you can't eat is the squeal! So people ate pigs' trotters for the same reason they ate brawn and all the other bits of a pig you probably wouldnt want to think about- no waste. Nowadays, there's something of a revival of the 'no waste' thinking amongst some people - their attitude is if you're going to kill the animal, at least have the courtesty to eat it all. Not my choice - I eat the bits I like - but I can see their thinking.