This would be exactly the same with paper printers.<p>"You can't print and bind books!"<p>"You have to order paper and ink!"<p>"Printer paper and ink are much too expensive!"<p>"The printer you buy will become out-dated too quickly!"<p>"Home printing does not leverage economies of scale!"<p>For something you can pick up at the supermarket for a few dollars that requires a lot of printing/materials (a book) it doesn't make sense. For something you can't (custom items, small parts, little toys, ...), home printing is (or will be) great.<p>3D printing doesn't have to meet every use case of commercial 3D printing to become very prevalent.
I don't know if we'll ever reach the "in every home" mark, or even say 90% of homes. This is different from computers for a lot of reasons. However the prevalence and wide-spread availability of 3d printing makes perfect sense.<p>Look at it logistically - if the cost of transporting bulk finished goods rises to a certain point, it makes more sense to just ship containers of plastic pellets, via slow and less reliable methods. Then local caches of the pellets are used in local printing facilities to make whatever. I can order a part, widget, or doo-dad and pick it up anywhere, or delivery by guy on bicycle happens, or whatever.<p>3d printing just has less waste and shipping overhead than making goods and sending them to a destination half way around the world.<p>There are price points where 3d printing makes more sense logistically than injection molding. I don't know what they are, but basic logistics suggests it is true.
May want to rethink your proposed hurdles. Printers are too small is purely a function of utility. If the use case changes the technology will change. There's not even a technical hurdle to bridge. It's simply form following function.<p>Your raw material issue is slain by the same slingshot.<p>The rest of the argument kind of falls apart after that. No disrespect intended.
As an aside, I've talked to a number of people involved with manufacturing and product design who use 3D printers for prototyping. Not a single one of them believe that we'll have 3D printing factories at home (although one of them did mention that 3D printers might be popular as toys).
Compare with laser printers. Similar objections.
I imagine when the 'printer head' becomes an integrated circuit, and the materials become the equivalent of toner cartridges, we'll see rapid adoption.