I know a couple of instructors that teach sidemount, but to be honest I see very few diving in my locale, where on a boat of 10 divers you might see one or two on sidemount. This year over my past 21 dives I've only seen one diver using sidemount.
For shore diving the Saudi (and Egyptian) Red Sea where the walkouts to the reef edge are 100-200m and as far as 2Km in places I'd want tanks on my back.
Sandy shore dives are probably easier for SM.
Really depends on the shore diving.When SM diving from shore, you take the tanks to the water's edge one by one and then get into the water and pull the tanks until in the proper depth to put them on properly. It is much easier to do that than 2 tanks on your back in BM configuration.
For shore diving the Saudi (and Egyptian) Red Sea where the walkouts to the reef edge are 100-200m and as far as 2Km in places I'd want tanks on my back.
Sandy shore dives are probably easier for SM.