Because printers generally just worked and buying OEM expensive refills was a temporary discomfort that, if it bothered you enough, you could work around by getting third party refills and save some money.

But since they’ve started locking down printers to reject refilled cartridges and third party cartridges it’s come to a head and people are looking for alternatives.

3D and CNC are entirely different animals, for multiple reasons. There were pretty much zero hobbyist devices and the available ones were so far out of reach that nobody could afford them except prototyping labs or manufacturers. The hobbyists did most of the legwork making 3D printers and home CNC work before manufacturers decided it was worth getting into the technology. Nobody needed really needed them like paper printers were needed for everything from school work to everyday business.