There is viable market (it has customers). But I would say it is just nostalgia. Some people even say it is not real ThinkPad unless it was made by IBM (pre 2006).
I love the keyboard and trackpoint, and older Thinkpads are rugged in a way that new models have apparently given up on. I bought the Thinkpad 25, which was basically a 2017 mid-range laptop with the old keyboard. It's adequate, but flimsier and less reliable.