Consider the "car." From the ground up, I've got rubber tires with metal belts. Rubber needs to be vulcanized. Of all the pieces of the car, this one is most applicable to 3d printing and I've still got to weave my metal belts (which have to be made out of steel, which has to be run through a drawplate to make wire, which has to be woven to make cord, which has to be woven to make belt) to put inside my 3d printing, which is going to bond poorly, and besides, I'll get maybe 100 miles out of those tires with the matsci we've got now. Sure, maybe in 20 years we'll have polymers that are more badass but rubber is still easier. Next we move up to the wheels - I can either CNC machine those out of aluminum billet, I can drop forge them out of molten aluminum, or I can stamp them out of steel. If I machine them I'm not inducing any additional forging strength so the aluminum has to be thicker. If I forge them out of aluminum they'll look cool and if I stamp them out of steel they'll be cheaper; either way, I'm looking at several hundreds of thousands of dollars worth of fab equipment. The billet aluminum ends up being cheaper and a lathe/mill combo capable of making a wheel for a car is $10k on the used market minimum. Now we're to the brakes and the hubs. Those have to be forged steel or else everything goes to shit. Not only that, they have to be metalurgically treated nine ways to sunday. The brake pads? An exotic combination of metals and ceramics, bonded at high heat and high pressure. We're already at some pretty goddamn extreme foundry processes and we haven't even made it to the car yet. Sneakers? So long as you're happy with crocs. You could 3d print crocs now. But shoes you want to wear? Any sort of fabric has to be woven, and any woven fabric needs to be sewn. Yeah, you can design it in something like this: http://www.youtube.com/watch?v=bWqS-1F3rjY ...but once you're done, you're still getting out the scissors (or laser cutter) and sewing machine and doing a fair amount of hand work.