The big companies now controlled all the major radio markets and could format the stations with proven, profitable programming. So the stations in all the markets were essentially the same even if that particular format wasn't really what the local market wanted. There weren't any small, independent stations left to fill the void anymore.
Then they started expanding the number of minutes of commercials played every hour.
Without local stations, there is no authenticity, and radio stations end up as money-driven instead of having an initiative. It's unfortunate, and I find it dehumanizing that commercials dominate the content. It only conditions people into paying more attention to certain brands.