What bothers me is, people washing and scrubbing their frying pans.

I cook in stainless, and after done just put it in the sink with water. After I eat the food, maybe a half hour later, just dump the water and wipe it with a rag.

Point is, why remove the grease, why remove the seasoned crust on pan. Do people take soap and scrub brush to their bbq too?

You don't need to soap wash, or scrub a frying pan.

This sort of behaviour likely keeps leeching to a minimum, compared to vigorously scrubbing and cleaning each use.