There are roughly three categories:

1) There's a bunch of commercial software which only runs on OS/2. A lot of it was vertically integrated software either developed for a specific customer by IBM, or developed in an "IBM shop". The ticket machines for the New York subway were powered by OS/2 until relatively recently. There are also supposedly a bunch of banks which have OS/2 dependencies.

2) There are still hardcore OS/2 fans who use OS/2 as their main OS. As you correctly assume, getting something like a modern web browser to run on OS/2 is a challenge, but some people grin and bear with it anyway.

3) Strange people like me who run things like OS/2 on spare computers or VMs for the novelty value.