Mortars cannot be transported by trucks or other vehicles?

[ai_beyondcontrol]

I get into the game just recently and I think generally it's one of best WWII real-time tactics ever. However I found it confusing that mortars, except for a few large-caliber mortars, can neither be towed by nor be loaded onto a transport vehicle such as a truck, which seems to make no sense. Do I miss something from the tutorial, or it's just how the game mechanics works?

[Saxhorn]

The 120mm can be towed any of the others need to be walked around by the crew.

Being able to transport MGs, mortars and other "light" support weapons was requested/suggested in a dev Q&A but to date it doesn't appear to have moved past the "we'll think about it stage".