Why is San Francisco Bay Area terrestrial radio largely impenetrable to independent musicians ?

Riddle me this --

Why is San Francisco Bay Area terrestrial radio largely impenetrable to independent musicians ? Compare this current situation to what existed here, twenty years ago.

A cursory review of regional playlists reveals a preponderance of major record label influence. How exactly does a for-profit business entity go about manipulating what we hear on the radio ?

Which begs the question: are record labels of any genre a seal of quality ?

Here's the thing that the alleged "majors" don't want you to know. Terrestrial radio transcends digital music platforms on the internet. The chances of a sale -- a physical CD, or otherwise -- suddenly becomes a distinct possibility.

A single, well-placed recording on terrestrial radio suddenly removes you from a highly turbulent sea of direct competitors.

The following article specific to the concept "independent promoter" might provide some direction here. Record label hires an insider, for a fee, to promote its current hotshots -- https://www.rollingstone.com/music/music-features/pay-for-play-how-labels-pay-songs-radio-871457/

No, I'm not about to fund the regional jazz or classical station's preferred insider, even if it represents a net loss.

Any costs advanced are best directed towards continued music research and development. To be sure, it's a challenging process: months / years of practice, hire the hall, the studio and highly skilled engineer, then press a limited number of discs.