Back when we could get both "home" and "work" locations through the diary, we found in an extensive multi-market study spanning several years that 80% of fixed location listening is in the 70 dBu contour and 85% in the 65 dBu contour. While "the 60" may apply for in-car, even that is doubtful.KFNC isn't dominating the market, but it is still a 100 kW that covers more than 2.6 million with a 60 dBu signal or greater, which probably puts it easily in the top 5% of FM stations in the entire country.
I saw about $70 million wasted in New York City based on "the protected contour". However, the target audience all lived at the edge of the 60 dBu signal where it was barely listenable. The station was sold about two decades later at a loss of over 90% of the purchase price.