The American consumerist economy is already heavily driven by keeping up with the Jones's. Why would that change just because we let people that can't work eat, shit in a toilet, and sleep indoors?

Yes, teenagers can be lazy and get stuck in unproductive situations. Some adults even can! That doesn't mean that's what the majority of people want to do, and there are more effective ways of getting people unstuck than turning off their power and evicting them!