While I understand and (for the moment) agree with your point, this was most certainly true of computers in their infancy as well. Most people had no context to assume that computers would take off and become ubiquitous and vital to so many parts of our lives.

It also takes a lot of time to conceive of/design a program, develop or have someone develop it, debug it, distribute it, and get people to download and install it. But this has happened, and on a grand scale, due to a steady progression of improved demand and increased efficiency of supply.

I do not mean to suggest that 3D printing will find the same reach as computing, or in the same way. I simply mean to point out that we do not yet have the perspective to see where it might go or how it might make itself indispensable (or at least invasive) on a commercial level.