The main use for my printer is maps for trail running. A custom map produced using OSMaps, some copy+paste magic, with some added notes (navigation hints, checkpoint cut-offs & other pacing notes, emergency numbers), printed on a couple of A4 or A5 sheets of "indestructible" paper, is much more convenient than carrying the full map of the area, or two maps if your route falls over a boundary.

Yes, most of us use GPS watches and have detailed maps on our phones too, but tech can & will fail and when it does while you are a little off course you'll be glad you have the paper map (and, of course, the ability to read it).

There is no need for everyone to have one though: I'm happy to print copies of my maps for others, I know a few people who don't have a printer of their own (they tend to use one at work if needed, or like your suggestion a local library).

I also like printing some things to read and scribble notes on away from the screen. e-ink implementations of this sort of thing are either expensive, so I've not tried them, or smaller than I'd like, or don't work well (big, inexpensive, works well, pick at most two).