When short burst of energy is required as in sprinting, anaerobic metabolism augments the effort that can be made. This is a survival mechanism for animals such as antelope that depend on speed over short distances. The cheetah also need a short burst of energy for survival. Anaerobic metabolism is an important temporary supplement to aerobic metabolism.
Anaerobic metabolism does not produce lactate, it produces lactic acid. It contributes to acidemia and consumes bicarbonate and so is a metabolic acidosis. It is commonly stated or written that anaerobic metabolism produces lactate and ignore the production of a metabolic acid.
In terms of the efficiency of carbohydrate metabolism glucose is converted to 2 lactate(lactic acid actually) via the anaerobic pathway. There is still energy left in the lactic acid. Aerobic metabolism completely consumes a glucose molecule. The antelope might perhaps have to graze a little longer if he survives. The sprinter if he wins the race might perhaps have to eat another donut.