If you really need more trucks reinforce other platoons with 'mobility' and borrow the trucks.
For some reason I do not have this option in campaign. Even 4th motor once I swap trucks for other things, they go poof. It maybe a beta bug or it may not. But even then, gun units would have some sort of transport for their guns in that unit. A truck, an artillery tractor, some kind of prime mover, or horses/mules. Big things like large howitzers are to big to move about without something to move them with. Although I am mainly thinking about things like pak 40's and zis-3/f22 guns. In fact in campaign now, only 1 unit has access to trucks under mobility. And that one does not need the freaking things. SU152's do not need trucks.
I just find it odd that things like zis 3 battery has no transport in the unit at the get go. And you have that artillery tractor that is not even in this campaign anywhere. Even with historical units off. Although those should probably be with the M30 howitzers and not guns.
but I am guessing many folks are not attempting to use their guns aggressive like. I sure did not the 1st go on this campaign. But the towing feature is just so neat and you can not readily use it. Still, my hold in South and Center with nothing but guns, infantry and light tanks is working great. And 32 guards is having a field day North West of stepkenovka. With tanks from 22, 5th, and 6th guards in reserve. Just now its night and infantry needs to catch the hell up. Not driving tanks around in the attack at night. Learned that last battle where I seemed to run into every German in campaign with anti tank grenades. They actually ran after my freaking t60's and t70's as it was dark, they got some. Experienced enemy really makes German infantry quite good. Well a lot better at any rate. Wish there was an option to up both sides skill. Infantry units behave quite different when they get above 70 or so experience. Better still, a user controlled slider for sides experience. Set mine to like 75 and enemy to 85.
I do agree that the largest pieces, howitzers and the like should come with tractors etc as default, How else did they get there?
Some platoons seem to be more likely to receive trucks when reinforced for mobility, it works a lot better in the battle editor to be honest, where you see each squad/vehicle listed, it would be nice if this system or similar was introduced into campaign reinforcement.
Another way to do this would be if we could move individual squads/vehicles between platoons during the operational phase, for example take a truck from command platoon A and attach to AT platoon B.