I have not found it to be common in any of my travels, however, if wanted, a dedicated divemaster could generally be found for an extra price. The other thing that can happen, is with a smaller shop, there may be just the two divers signed up for any given dive . . or in any event, a smaller number of overall divers, than if they go with a larger shop.
Some divers just hang really close to the diver master, which often works out fine because other divers like myself, prefer to be way at the back of the pack (out of the crush, so to speak).