Bret Devereaux writes here about the oddities of the academic job market.

His piece is comprehensive, and you should read it, but short version: professors are split into tenure-track (30%, good pay and benefits) and adjunct (50%, bad pay and benefits). Another 20% are "teaching-track", somewhere in between.

Everyone wants a tenure-track job. But colleges hiring new tenure-track faculty prefer newly-minted PhDs to even veteran teaching-trackers or adjuncts. And even if they do hire a veteran teaching-tracker or adjunct, it's practically never one of their own. If a teaching-tracker or adjunct makes a breakthrough, they apply for a tenure-track job somewhere else. Devereaux describes this as "a hiring system where experience manifestly hurts applicants" and displays this graph:

https://astralcodexten.substack.com/p/why-is-the-academic-job-market-so