Maybe someone else can chip in. I cannot recall seeing the Jeep being abused in 3v3. The reason why it lost its crew is also a different one.
My point still stands: The WC51 can transport units, it even comes with close range cav rifles. Outside of 1v1 streams and tourneys, I have not seen this being used/abused.
I still very vividly remember Chav drivebys. You'd decrew the WC51 so the UKF player with his CP0 ass tommies could tear enemy players a new asshole without ever having to leave the vehicle. Something USF can't do for another CP.
EDIT: I don't play 3v3 so idk but 4v4 this was a very popular (and incredibly f*cking effective) tactic. Many tasty MGs were stolen..