(Didn't add the quote, but this is a reply for MARK)
Designing models is pretty complex.
Not only do you need to create a model, you have to make it printable.
This is more or less the same process as making models for PC, but there are more technicalities involved.
Empty spaces (what they call "overhangs" can be a pain in the behind) are the toughest to design. (ypu can also use disolvable materials where the empty spaces are)
Then there is shrinkage (depending on the materials used). Specially long and straight parts are hard to keep straight (they warp when they coold down)
But before you even get that far, you want to have control over your printer and used materials (which all respond differently, on different temperatures and printing speeds etc.)
Even the thickness of the layers needs perfect calibration (a mathemetical perfect cube will come out with uneven sides when not properly calibrated)
When I bought mine, I already did a lot of research, but I never would have guessed how complicated and precise this work is.
Even downloading a fully printable model and printing that is not as straight forward as I imagined.
Your printing bed bed needs a good surface on which the material used sticks to. It needs to be flat. It needs to be exactly level (deviations from level only show when you have printed multiple layers, and it get's worse the larger the model is).
A very rough guess/estimate would be that in 5 years time, there will be printers which are good to go, straight out of the box.
Most printers that are available now are too complex for regular consumers.