I have a house rule where infantry units will always hit a vehicle in melee combat, because it makes sense for a target as fakhueg as a Lem- Battle Tank be an easy target in melee. Anybody else also do this?
I think you have to imagine that the vehicle is not static. Attacking a target that may crash you is dangerous, and this limits the chances of an effective attack. Moreover the attacker looks for a weak point, and to do it on a moving target able to defend itself by moving, or with the weapons of the crew it is all but easy. It's even worse if the target is an antigrav tank or a combat walker.