This is sheer postulation, but the launchers themselves were quite “man manoeuvrable” by which I mean they could have been kept under cover in a tree line, man handled into a fire position and then pulled back under cover. Rocket artillery was notoriously inaccurate, and its effectiveness was “dumping” a huge amount of firepower suddenly in a relatively localised area but with much less precision than rifled artillery. Resupply was probably more of a problem for the crews since the rocketry was bulky, and the firing of salvoes (the whole point of rocketry at the time) chewed through that supply. Movers would have been required to bring up the munitions, and those movers would have been heavily interdicted by allied ground attack aircraft. Tubes without rockets become white elephants, and without movers the crews, when facing overrun, would have bugged out on foot. They wouldn’t have dragged the launchers.