During the so-called "top 40" era (an arbitrary label and not the actual number of songs on station's playlist) playlists got shorter during the 60s, most notably on stations following the Drake-Chenault version of the format). More important, playlists were more diverse in musical styles. "Top 40" stations played MOR, country and R&B cross-overs plus Oldies. Fewer stations. Bigger shares. The game was to please all of the people, some of the time. When broadcasters were forced to stop simulcasting on FM, the result was more choices in the market (and new formats). Then the game was to please some of the people, all of the time. Further, with stations competing directly for the "top 40" audience, stations tried to minimize tune-out by playing stuff that was "too different."
Much the same happened in talk radio. Up to the early 90s, talk stations included hosts with various political viewpoints as well as sports, personal advice, financial advice... When Rush started on WABC, his show aired between Lynn Samuels and Joy Behar. KABC back in the day had room for Joe Pyne and Michael Jackson.