Guffe said:
Hell no!
As you said, they don't want it and you take the risk to steal it. You get it and it's yours.
I mean case in point BF is supposed to be somewhat "realistic" shooter, well you don't see people moaning in real war about cheating if someone steals your vehicle. If you fight 8 on 8 first to 50 in war game... There's only one rule. = Any means neccessary!
You also don't see every run of the mill frontline soldier knowing how to operate enemy machinery in real war either.
OT: Taking an abandoned vehicle? Great. Do it.
Taking a vehicle inside a contestable area? Great. Do it.
Taking a vehicle inside an uncappable base, like one that is obviously meant to be a primary staging area? Hell no. It is bad game design if you are able to. There would be guards and sentries and other failsafes in such a base, but these are difficult to program, and no one wants to be stuck with base duty when they log on to play. Add to this the fact that it is much easier to get away with a vehicle because it is a game, not a simulator, and the resulting situation is that it is much easier to make off with hardware from what should be a very secure base than it should be.