It's not that often when you capture a piece, usually it's destroyed, so it won't be that commonplace. Capturing something implies you can use it for yourself, so why not make use of this? It's a prominent column on the scoring table, and sometimes I actively try to capture some pieces, but then after the battle it has no effect? A bit strange, don't you think?
I believe it would add to the realism angle of the game, just like scavenging weapons does. Those are pretty advanced game features. It could be limited with a limited ammo supply for example, or with a 'chance' factor of getting the thing to work. For the non-likers, perhaps this could be in the 'options' screen: "Use captured enemy vehicles/guns" check box.
If it could be modded, then maybe the modders out there could think about it.