Well, it doesn't just boil down to ratings...it boils down to demographics.
Most AM stations have few, if any, listeners under the age of 40. Admittedly, I have not recently seen
demo breakouts on WLW, but one could assume that, in at least some respects, they're showing some signs
of what the business calls "greying". And, if so that's the bigger issue.
If your audience gets "too old" (in the minds of advertisers), they don't buy you...or...they demand lower rates. Both would have a negative effect on the revenue picture, obviously. And certainly would stress any AM station PD.
Why have "oldies" stations largely gone away? Either they became classic hits (60's/70's/80's) to lower their demos, or they switched. Same reason.
AM radio ain't getting any younger...and neither is its' audience.