You hire a PhD if you need someone that can do research. It's a bonus if you find an exact match to your research area, but it is certainly not a strict expectation.
Of course if you can get a 400k software engineering job, you’re going to choose it over a 140k research job in your field.
My coworkers are all PhDs, people whose PhDs were in topics like QCD working on completely unrelated computational physics, various biology, chemistry PhDs doing experimental physics, astronomy etc (and vice versa). I am considered strange for still working on the same topic as my PhD.