Because it is a convenient food source, for those that can digest it. Being able to digest lactose is more common in people whose ancestors domesticated cows. H

Because it is a convenient food source, for those that can digest it. Being able to digest lactose is more common in people whose ancestors domesticated cows. Human evolution has not stopped; the ability for some people to digest lactose into adulthood is a recent adaptation, which happened after we domesticated cows and had a convenient food source available, aside from their meat. A cow's liver also serves a very specific evolutionary purpose for the cow, but I've never seen anyone say, "Why would anyone think of eating a cow's liver, evolved to detoxify the cow, not feed people?"