Isn't it dependent on circumstances, though? Suppose the airline has a flight that goes A to B and back to A with the same crew. It doesn't have enough PAX on either leg to make it a paying proposition. If it cancels, it saves the cost of fuel, landing fees, flying pay, ATC fees and maybe hotel and subsistence costs, and who knows what other charges. Quite possibly catering costs, too. There must be a maintenance aspect in that the aircraft does fewer landing cycles.
So under that particular set of circumstances, it's worthwhile cancelling - probably even after paying EU compensation! Especially if you can consolidate the pax with those for the next flight two or three hours later
Take the other extreme where the aircraft is needed to go A to B to C and the flight crew B to D, the cabin crew B to E, and the situation is as Northbeach describes.