It is ASTONISHING how much oil flows in an engine. The oil has an important function of taking away heat, as well as lubricating, so a lot of it needs to be kept moving. A typical stock oil pump will empty the oil pan in seconds at anything above idle (if there was insufficient return oil).
This is why oil drainbacks and baffles are so important. You've only got gravity to get all of that oil back to the pump pickup. Under normal operating conditions the pump will hardly bypass at all, so it's all going OUT!