One of my customers still has a Netware 3.12 machine. I'm the third person to be responsible for it. The last two guys are both retired now. I got the gig based on being the youngest person the company could find who actually knows Netware. It runs their ordering/job cost/inventory systems and whatever files or reports it makes can actually be used by their relatively modern accounting software.
Another guy I do work for has a System/38 machine in his office. I have no earthly idea what he does with it since he's a primarily a studio photographer, but I have seen him accessing it through a terminal session. My best guess is that it has something to do with his home-made film printing system. He was an engineer for a while and his place is full of cool stuff.
I've also been in law offices where secretaries were still using Windows 3.1 as recently as 2013, but in that case I'm pretty sure it was just the lawyers in question being just THAT cheap.