system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why don't we inhale close to (or all of) our lung's capacity worth of air when we breathe naturally?

In other words, why isn't every breath a deep breath if our lungs can handle it?
(Assuming we don't put a great deal of consciousness into breathing.)
gpt
Life has this tendency to want to do the thing that takes the least amount of energy(for the same result). It takes a lot of work to fill your lungs to capacity, and it isn't like all the air gets used by your lungs in either case.