As far as I can tell the support for them wasn't dropped from the engine (the system, along with custom location names that Bungie was working on for map variants, are all there). So why did they not include it in H4? CA wouldn't need to worry about plastering area names on the walls to keep players from getting lost if 343i would have kept with a standard way of giving naming locations around the map (which were always visible on the hud mind you).

Having standard names keeps everyone using the same callouts. Makes for playing with randoms that much easier. Well, assuming they can read to begin with.