A lot of hobby level 3d printing is like this. A good bit of the popular prints are... things to enhance your printer.
Oddly, woodworking has its fair share too - a lot of jigs and things to make more jigs or woodworking tools.
The problem is two-fold… abstract thinking begets more abstract thinking, and the common advice to young, aspiring entrepreneurs of “scratch your own itch” ie dogfooding has gone wrong in a big way.