The problem is not 3rd person view, but rather making the vehicle so maneuverable that you can just whip around and kill anyone sneaking up on you, which should not be the case. The real reason you pretty much HAVE to have 3rd person view is simply because it’s a game, and as such can’t provide you with the 170 degree FOV that your normal eyesight provides you with, combined with the ability to move your head around without drastically hampering gameplay (as most vehicle controls that allow you to look around while you drive do). The most obvious and, more importantly, most practical solution is then 3rd person view.
The problem, as has already been sighted, is that you can see behind yourself with that, well, you can see behind yourself in a vehicle in RL, and much more efficiently I might add, so there really is nothing wrong with that aspect of it. No, the real problem lies with being able to maneuver the vehicle so as to deploy deadly force on the person attacking you, which you wouldn’t be able to do in real life, at least not in a way that wouldn’t be easily avoided by the attacker.
Besides, if you are attacking a vehicle, it should be from far enough away that he can’t see you behind him anyways!