I'd say it was partly geography, since you can't put many 50 kW Class A stations in the middle of the country without precluding a large part of the country from using the frequency. And a 5 kW fulltime station like WDAF, being nondirectional at night, and well protected, was good enough. WTVN isn't bad even though very directional at night, as was WTMJ with 5000 DA-N. Really, the mid to high dial position 50 kW Class Is/Class As above 1100 kHz, and particularly above 1500, really start to suffer from smaller groundwave coverage. So even a good 5000 watt low dial position station was good enough. KCSP (WDAF), KCMO, and WHB are certainly facilities that most broadcasters would like to have in their cities, though perhaps not so directional at night.