This doesn't obiouvlsy need to be an high priority.
Probably those vehicles will only be used in RPG gamemodes, but just for the sake of immersion if would be nice to see them during SP/MP missions.
I remember about A2 campaign, where the city were filled with those vehicles, it gave more realism to the ambient...plus a tractor in Altis seems to fit quite well !
- I know there are MODS for that, I just want them IN THE GAME, like old Arma games had. -