"Why Don't We Eat Rat Meat Everywhere If Rats Are Everywhere"
https://www.youtube.com/watch?v=xI94lZV-KbI

It's a good question and the explanation offered is legit. However, when it comes to efficiency, they lose to the chicken for the same reason as edible insects and other meat animals. Chickens lay eggs. Cows can provide milk. Almost everything else is just meat once and more of the same animal when reproducing. Pigs are economical due to their size and diet, despite producing nothing else.