Mostly in Europe and Africa. When we stayed in AirBnBs in Europe we've met the host almost every time. One helped me park my oversized rental van and then paid for the parking since it didn't fit in the spot that came with the house. Another was there to show us all the amenities. Another was there to tell us to pretend we were his friend because rentals weren't allowed. And the one in Africa did a whole grocery shopping for us because she knew we were arriving late with kids and wouldn't have any food to feed them in the morning.

But yeah I've only ever met one host in the USA, and that was because they lived next door.