We drink dairy milk because our culture has evolved along with dairy cows themselves. Maybe in an alternate timeline we'd be milking dogs. The cultural connection is why people are so attached to their meat (me included).

As a member of an older school farming community, livestock make natural fertilizer and meat from grass, bugs, and surplus grain. They play an important role in completing the nutrient cycle. Meat ends up being a bit of a luxury (limited quantities), but it's a product of sustainable land use imo