I don't think these are for every household. Right now a 3D printer is incredibly useful if you're really willing to put in the work to learn, optimise, and even design your own parts.

Joe soap is never going to do that or even want to do that. He doesn't even have a need for parts, after all he doesn't repair his stuff, he just throws it away and buys new stuff.

Perhaps he'll buy a 3D printer when he can go to Amazon and click "print" instead of "order". But we're a long way from there.