Before the radical changes in radio regulation of the last three decades, including Docket 80-90 and the ownership cap limitation removal as well as license renewal requirements, we had to promise a certain number of PSAs per day and per week to get a license renewal.WHVN in Charlotte NC came back on the air after being off for several months, and it took several more months to sell the station. I couldn't pick it up at home but I wished I could have. No commercials. Just PSAs. Someone on this site said they weren't helping and, in fact, I was told if you could hear PSA's on any station during a time people were likely listening, it wasn't doing well.
Some of us realized that a 10" liner counted for as much as a 60" recorded Red Cross PSA, and did them all "live and local". And then we pretty much quit doing them at all. But for decades, those PSAs were very much a part of securing license renewal... just as newscasts and the "Sunday Morning Shows" were.