I think foam soap is quite capable of doing an excellent job of degreasing your hands. As to why hotels use it -- I wonder if the economics kick in. It seems to me that liquid soap is an immense waste, the way most people use it, they dispense three squirts, most of which misses their hands, and then wash for 3 seconds. I don't think the soap is that expensive, but not having to pay for personnel to refill the containers mid-day might be a worthwhile saving?