These days having only one core business makes not only the company less attractive to lenders/investors, it makes the company vulnerable to adverse changes in that small universe. Our various conversations on this board where Walmart has replaced the local grocery stores, Home Depot the local hardware stores, and on-line auto sales is eliminating the local car dealers is just one small example. All these businesses were the bread and butter of local radio. You can still be in the media business and be attractive to investors, it can't be just radio only.
As David mentioned in another thread: You can have great ratings in your core demographics, your station is always on in the local salon, the community loves you on a regular basis, but if there are no advertising support around all those listeners, you're fighting an uphill battle which ultimately you'll lose.