[Imp]

My thoughts but remember its a game so fun can prevail but use common sense so.

Capture a basic vehicle like a truck.
This is Russia in the 40s how many people have driven 1 or know how to maintain it carry out basic repairs.
Your farmers probably would be the guys if lucky enough to have a tractor, otherwise the guy that drives the truck picking up the produce lumber or whatever. Everybody else? Vehicles were not exactly a common thing in Russia at that time.
Now give them a tank, its probably going to pack up due to abuse & really would be better suited to use in a scenerio as you would edit experience drastically down.
The guys probably just got the hang of driving it when it packs up & the gunner can't practice because he only has the ammo in the tank.
It certainly would not be second nature like driving a car becomes so in fact the lack of skill means they are in a mobile coffin.
The same goes with infantry weapons including guns, they can probably fire reasonably well but they will breakdown or run out of ammo.
Hope that makes some sense but I think troops generaly stick to there own weapons occasionaly using enemy stuff for that engagement but soon getting rid of on the whole.
The reasons are as stated he has an ammo supply, knows one hopes how to maintain it & has used it more often so is more comfortable better with it. The better the soldier the more likely he is to be able to use & maintain diffrent equipment well.