Venous and/or lymphatic systems use muscular contraction and movement for fluidity. It is specially important to counter gravity. The "need to move your lower e

Venous and/or lymphatic systems use muscular contraction and movement for fluidity. It is specially important to counter gravity. The "need to move your lower extremities" is a natural instinct. So it's not "an engineers thing". I'd say it's not even a "humans thing". Try "animals" (with lower extremities and veins and/or lymphs). Disclaimer: I'm not a doctor or a vet.