Frequently there aren't. The subject of this article is an artist, so cue your STEM lord "do you want fries with that" jokes now.
However, this can occur even in fields like math and computer science. You graduate with a PhD in math and a specialization in topology. Who will hire you to do that? No-one. Plenty of people will hire you to do something you can do, but what if you really want to continue research in your specialty?
I'm working on a PhD in CS with a specialization in programming languages. Google came to do a PhD recruitment day and essentially asked "so what kind of PhD are you getting, machine learning or systems?" and we said "programming languages" and the reply was "wow what is that?"
So if you want to work in your own specialty, you might need to work in academia.