Congress bickered for years about this. Rep. Griflin of New York went as far as to compare radio operators to train engineers, who did not need licensing. But there was a catch. In that era radio was beginnign to play an important part in marine safety. Because of this it was decided that radio stations and their operators should be licensed. Through the years, the required qualifications for a broadcast transmitter operator have varied.
During World War II, there was a shortage of radio operators with a First Class Radiotelephone license. The FCC was forced to permit operation by lesser grade operators with an amendment to the Communications Act of 1934. For the next 50 years most midifications were meant to address technological improvements.
But these slowly reduced the testing rquirements of the operator. (Ex. Automatic transmitters dont need DJs to do the switching. ) So by the mid 1990's , the FCC had reduced the requirements for an operator license test to what ammounted to a registration, not a license per se.
Since this provided little value in insuring the competency of broadcast station operators, congress authorized the FCC to waive the licensed operator requirement with another amendment to the Communications Act of 1934.
On a personal note, I clearly remember the very confused college freshmen DJs that Fall having heard about the FCC license and in many cases haveing even seen them in orientation being very confused that it was no more.