because it is the natural thing to do...we are optimized to do exactly that.
The industrial meat production is a other topic...that is wrong, unhealthy, cruel, environmental damaging. We should ban that as good as possible, but we can have everything full with goats, cows, pigs.
When I see what many people (not even thinking for restaurants) throw away on eatable food, a few houses together could easily have 1 pig and some chicken.
Maybe not having every meal some meat, but when having it having something in good quality.