We're doing everything we can to keep armored warfare out. That's why we stopped the Communist Mecha: such things would pave the way for PANZERKAMPF, which while being fucking awesome is not the focus of the game at first.

Also, it could not be reducing mass, otherwise people would know, because if mass was reduced not only would the laws of physics be out the window [even more so than now], but also collisions would not be a problem in the slightest.