User blog comment:Warmachine375/Gun-Gun Weapons possibility?/@comment-73.136.18.37-20150530152820/@comment-25555436-20150530234454

No one said anything about substituting the real tanks. They can be used as such and were used as such at times, but they never substituted them.

The reason it's size is good is that the role of a tank, their real role, is to be a mobile shield. To give big, resistant, constant cover to the infantry. The bigger the size, the bigger the shield/cover provided to the infantry.

Besides, tanks will by the end get destroyed anyway. In modern times, pretty much anything can destroy a tank. A grenade, a rocket, missile, bomber...hell, even just moving is enough to ruin it. As it's going to be blown up anyway, it's remains may well give bigger cover to the rest of the infantry compared to a normal tank.