I sometimes use my 3D printer just so I can get the thing right now. For example, I once printed a small electrical box, the kind you can find for $2 in any hardware store. Totally not worth it in normal circumstances, but it was Sunday, shops were closed, and I needed one, so I just printed it, and finished the job, didn't have to wait the next day.
And you got things wrong, 3D printers don't print bottlecap openers, they print little boats ;)
I had to print some little "brackets" for the blinds in my daughter's room after she broke some (she's a toddler) and we needed to close them for bed time;
Half an hour in CAD and another half an hour of printing a dozen of them, and now I can replace them any time they break.
I also printed some curtain clips for my wife rather than drive to the DIY shop or wait for Amazon to post me some; Perhaps not cost effective, but better than driving a couple of miles for £1 of plastic clips?
I have young children so I occasionally print aesthetic things, but as a rule, I reserve 3D-printing (or "printing" as my daughter knows it because she's never known printing to have fewer than 3 dimensions) for practical things.
It's funny, my wife has never been on board with my hobbies so much as she is with 3D Printing.
Are you talking about those blue outlet boxes? If so, those provide a lot of fire safety that your 3D Print does not. You really should rip that print out of the wall.
And you got things wrong, 3D printers don't print bottlecap openers, they print little boats ;)