The way it usually works, some jobs never get advertised, or get advertised only as blind-box postings so you don't really know who's looking for someone or where the applications go. (That way the EEO requirements are technically met, but who's going to be able to call them out when the rules are evaded?)
Other jobs get publicly posted but the station brass already has someone in mind...and one of the outside applicants just has to blow the bosses' minds (or get the attention of someone still higher in the food chain at corporate HQ) to get past him.
Still others get nominally posted in order to improve a station's EEO record when the station has no intention of filling the gig with anyone at all, but just plan a voicetracked or syndicated show.
It's a rare job that's actually truly open to a promising talent just tossing a tape and resume over the transom. It happens, but maybe only 10% of the time, when a station has an empty bench with not much time to fill it and no suitable or sponsor-acceptable satellite alternative.
It didn't used to be that way, simply because stations' standards were more consistent and more stations needed more live voices. The false economy of satellites and hard drives convinced front offices they didn't need those voices any more (and they clearly haven't yet drawn the obvious connection among declining audiences, stagnant revenue and canned programming, or seen how well companies that still do program live and local, like CBS, are doing generating profits Clear Channel and Cumulus can only dream of).