Of course there's some trim that has to go into the grinder, but we could do a much better, more respectful job of using the animal as it was instead of homogenized lumps of 80/20 or 90/10. More beef cheek in the butcher case and homemade cabeza, more lengua, more shank and round and plate, more heart and tripe and liver, etc etc etc. Buy a subprimal and grind your burgers at home from a single animal.

This is more a culinary and ethical argument than efficiency or safety. One should use the whole animal, in all its varieties, because they're delicious. Grinding otherwise edible parts of an animal killed on one's behalf because one disfavors (or is repulsed by) them seems to me much worse than the killing. Eat - and enjoy! - all of it or don't kill it.