Another way to look at the difference between 2D and 3D printers in the home is that if internet-based document printing services predated affordable and accurate document printers, then we would not likely see document printers in very many homes.

The main point of difference is that by the time it became practical to send files to a big centralized service, the printer had already become a normal (and cheap) addition to the household. Now that one-off customizations can be sent to a printing service practically instantly, the numbers stack up against buying a 3D printer for the home unless the buyer has an exceptional amount of stuff they want to make, or they want tight control of the files they print, or if they want to start their own local printing space for profit (which might become pretty common since small, local printing shops will have a moderate speed advantage over big, distant ones by virtue of shipping times).

Don't get me wrong, 3D printing is still going to be huge, there will be 3D printed goods in almost every home in America within five years, just not necessarily 3D printers themselves. Eventually printers themselves will be as common as the table saw, but those are very far from being an essential home appliance.