I recently came across an infographic discussing adjunct professorships. Even though I've been lucky to find a tenure-track position, I do follow a bit the struggles adjunct faculty members are having.
A few side thoughts to this infographic:
1. Doing a PhD does not necessarily mean you are studying to become a professor. There are many career options, in industry and consultancy to just name a few, and saying that only 1 out of 10 PhDs get the job they studied for is wrong.
2. Many adjunct professors see teaching as an additional job, and combine this with consultancy (especially in engineering). So the adjunct salary is often just an extra source of income.