It's mostly political, to wit:
The FCC also regulates TV and to some extent the Telephone company. Telco uses many microwave links and goes over the airwaves. Much TV traffic for networks and syndication goes through the Telco trunks. This was the traditonal domain of AT&T "Long Lines" and "Toll Office". The infrastructure required is massive and the heavy investement of competitors into fiber optics has concentrated on intercity wireouts, rather than "Long Lines". So I think AT&T still holds sway there; either way, where you find "Long Lines" you will find FCC Commercial Radio Operators Licenses posted on the wall. That is the Law.
Licensing is also different for public radio and public television, and for community radio and community television, as compared to commercial applicants and licensees.
That quote is in a writeup further down the wikipedia link that was listed.
There is less an issue with bandwidth or technical specifications here [Fairness Doctrine] than that the FCC gets into the business of running the stations. Part of this is the political clout invovled, i.e. does congressman Jones own all 5 Radio/TV stations in this district? You're new at this: can you demonstrate sufficient financial reserves to account for three years of operating at a loss so that your new station will survive in the market you have chosen?
On the technical side: OK, Mr. John NewStationPetitioneer, we've looked at your [mandatory] technical survey and those of the existing stations. There is no room for an addtional station at this time.
John NewStationPetitioneer knows there is a small station in financial trouble; his backer, Julius Megabux buys it for him. This is simpler than waiting for "someone to die" or 50 years for technology to change things. Suddenly John NewStationPetitioneer is back at the FCC offices for a Station License transfer. This shifts things back to the political front office and more scrutiny under such as the Fairness Doctrine.
Growing up, I knew station Engineers, my buddy and his father bought a radio station and I got one of those FCC licenses.
Mustang