If you look in the basin or on the counter below a traditional liquid soap dispenser, you'll find... a lot of traditional liquid soap. After decades of development, the industry has created a formulation too liquid to stick to your hands, yet somehow able to cling to the sink in defiance of torrential rinse water. A person will typically pump two or three times at such a dispenser, but most of that soap will typically slip promptly between the fingers.

Foam soap eliminates the waste and unsightliness of other restroom patrons' pink splotches in the sink. Pump twice and you'll probably get the same amount of cleanser as one crank of liquid soap, but it'll actually stay in your hand.