Because meat, done right, makes vegetables awesome and vice versa. Ideally you do your best to respect the life that ended to feed you though - that means trying to eat a lot (within reason) of a specific animal; eating livers, kidneys and hearts; using suet for pastry; a chicken carcass is boiled up to make stock. In my mind, it rightfully has its place in a symphony of flavour if you follow those rules of thumb.