They also produce much more meat. They also eat indigestible (to humans) food. Cows stomachs can eat and gain calories from grass in a way humans or dogs can’t, for dogs and humans grass is fibre and doesn’t provide many calories.

Cows are great in this case for food security, ground that would struggle to produce much grains or vegetables can still produce grass. If you feed your cows a lot of grains the food security aspect is nullified. Even feeding dogs grains for a country like North Korea that struggles with food security is not a rational unless the dogs provide a benefit like guard dogs etc. During World War Two many people in UK cities killed their dogs when rationing was put in place (not to eat) purely because it was suggested the pets would consume food that could have been human food.