I got the impression that the "drop-off" diving was really more of a convenience for the resort: they get to advertise it as part of the dive package without actually having to organize some other offshore dive. Over the course of a week, that adds up to 5 dives (per boat) that don't happen on some other part of the coast, saving on fuel and staff fees, assuming they're paid per dive.
Those drop off points are close enough that a small skiff could ferry divers back and forth all day long with little added cost to the resort, leaving the dive boats free to access much better dive locations.
I got a little fed up with the drop-offs too.