If we're worried about wasting parts of the animal, in a typical hog the blood is maybe 10% of their body weight. Significantly more waste (by mass) is created during the trimming process. If you want to do your part, you can buy a pack of "bits and pieces" whenever you need to render a lot of fat and don't really care what it looks like in the end. These trimmings are in substantially greater proportion than the finished bacon you typically buy. So, if you're making something like a big batch of beans, you can get the exact same flavor profile for maybe 10% the cost.

Sitting on a British Airways flight heading to NYC, tucking into a full-English which was tolerable but not great, I had a tap on the arm from the Japanese businessmen sitting on the same aisle, "excuse me -- what is this?" he asked pointing to the black pudding on his plate, "that's black pudding, a type of blood sausage" I replied, at which point he thanked me, turned a little pale and pushed the slices to the side of the plate.