Computers had evident uses people craved for even when nobody had one at home: coin-op arcade games for example drove huge crowds. Writers used electronic typewriters with small displays and would be better off using an editor program. And a spreadsheet was a killer app for any small office -- they already used calculators. Add communications and entertainment to that (mail, chat, www, video) and computers had tons of killer uses.
A 3D printer is a one trick pony. It merely prints stuff. (Well, a computer is a one-trick pony too, it just "processes information", but in the realm of information this amounts to infinite possibilities).
People that like tinkering and DYI will love one -- but they are not that many. The general public, not so much.
They can create any thing/part they want themselves? Well, the thing is, generally they don't want stuff created. And when they do, they can also have some factory create them somewhere and buy them. And even if they needed something extra-custom, they could order it to a 3D printing shop down the road, and be spared all the trouble of owning a 3D printing, managing supplies, learning the software, etc.
The analogy with the home computers is interesting, because people are even scaling down on buying home computers. The general public finds that the limited stuff they wants to do, they can do it with a smartphone and a tablet (and maybe an ultraportable, for the more needy).
Heck, tons of normal people don't even like owning 2D printers (and have always had lots of problems configuring and operating even them, as evident by any support forum).
I don't agree. The main obstacle for computers was cost and size, which naturally scale down as technology improves. Applications were already everywhere even decades ago.
3D printing on the other hand fundamentally has difficulty delivering many things people want it to do, and the things it actually can do are fairly niche. Mainly prototyping, to my knowledge.
If 3D printers could already print forged steel or 14nm transistors (but at great cost) I'd say the future is very bright, because cost and size naturally come down, but they can't do that yet.
There's been some work already into printing circuits, but I think it will probably look different than the traditional electronics we're use to thinking about, as metal may not be the only way to print circuits.
I admit that 3D printing is a long, long way off from this, but I'd argue that every item I bring into my home and every material purchase I make is a potential application of home/consumer 3D printing waiting for a solution.
