The problem with that scenario is that the mom & pop daytimer AM in East Broomstick you got your first big break on doesn't exist anymore. Mom & pop may still own it (corporate radio doesn't really extend to small market USA), but it's such a shoestring operation that there's probably less staffing than at a corporate station. 20-year veteran morning guy is also PD, music director, production director, chief engineer, traffic person & janitor. Add a few sales people and that's about it. Automation or satellite rest of the day. Cash flow can't support much more staff, and what 19 year old wants to pack up & move to Podunk for minimum wage? This is not a new problem, the roots of it go back to the late 70s/early 80s to some degree.
Even the markets that used to be the 2nd or 3rd stop on someone's career ladder are having trouble finding anyone remotely qualified...that's one reason the old timers are staying on. Of course, another is that there's nowhere for them to move onto either.