I'll put it in to perspective with the enemies: Fallen and vex have a teleport ability, cabal do not. Too bulky and militarised for it. (hive are primitive before a smart arse tries to put them in the equation). So a cabal with teleport doesn't make sense right? Same goes for the class. The titan is designed to be slow and armored, making it more mobile just doesn't make sense, of course if it were to be added I wouldn't have a problem with it, but it would just seem silly in my opinion.