Yeah, I could have worded that a bit better. The comment's certainly open to misinterpretation. A couple of folks up the thread have divined the meaning that I wasn't precise enough to make clear.
It's not that you can't build neat stuff with 3-D printers what I contend is, other then AR-15 lowers and high-capacity magazines, there's not much reason to bother. And even in the case of AR-15 lower recievers and high-capacity magazines it's politics that makes building them worthwhile; conventionally-manufactured equivalents are simply better in every regard, including price when you figure in the cost of the printer and the time you'd have to put in to learn to use it.
One respondent has a car door that won't open for want of a plastic part which is known to break. But buying a 3-D printer, and putting in the time to learn how to use the software to draw the part, generate the G-code and deal with the inevitable idiosyncracies of any tool is hardly the sort of solution that most people would embrace. If you were looking for an excuse to buy a 3-D printer that might make the cut but most people would simply buy two of the parts the next time they had to go to a junk yard for one and be done with it.
Another respondent brought up Visicalc which is the sort of thing I had in mind.
The first time those of us of a certain age saw Visicalc in operation is memorable for the harp-accompanied epiphany that results from the realization that a pathologically boring and utterly inescapable task will now evaporate. No one who had to prepare organization budgets had to be sold on Visicalc. It sold itself.
Budgets are still necessary but the only people who now add up long columns of numbers suffer from obsessive-compulsive disorder.
That's the sort of transformative change I believe is necessary to propel 3-D printing into society.