It's a kludge to address volume.
aha
also one of the conundrums facing vehicle minis ... how to show reasonable volume of vehicles. I designed a combat chopper that has 9 tons of infantry space (max is 10 basic troopers per ton right? platoon size is usually 27, but I like 30 man platoons). While it clocks in at 30 tons, I would imagine it would be a giant bumblebee of a target. Compared the direct combat chopper at 25t with a main gun and 2 MGs, no need to have a big open space to hold people so it would be slimmer and 'denser'.
I'd totally be ok showing that though ... What do you mean that thing is only 30 tons! ... Same reason a camper might weigh a lot less than the truck that's pulling it, but the camper can sleep 5 people while that truck can't sleep any (ok, sure, fit some in, but not designed for it)