Having worked in Radio (Medium to Small Market), I can honestly say that it has nothing to do with what the majority of people want to hear. It has to do with the "Mighty Dollar".
The people who own these stations usually don't even listen to them. They only watch the advertising sales and the profit margin.
From the owners point of view, in the KSJO station, Changing to the Hispanic format was a wise choice to capture the Hispanic spending trends. You will see much more of this because statistics show that the Hispanic population, especially the newly arrived population, spend money quickly and carelessly.
Step back and look at the type of music you enjoy. Then look at all the people you know that also enjoy that type of music. Now look at yours and their spending trends. Are you and your friends spending enough cash to keep the advertisers paying that radio station? Are you and your friends buying the new cars, the home furnishings, etc... that you hear advertised all day on that station?
Also keep in mind what the Owners of these big stations are thinking. They are buying stations with medium to large market potential. If the station is playing heavy metal and the advertisers are "Joe's Tattoo Parlor", "The Guitar Shop" and a bunch of national commercials (ie.. Ford Trucks, McDonalds, etc)... This radio station is obviously "Just getting by", because no one wants to advertise on it. Nothing wrong with this, if you own the station and you are happy with just making a living and keeping the bills paid. If it's a powerful station, these big companies will buy it and change the format. Their thinking here is simple. Heavy Metal people, for the most part, do not buy NEW cars every year or a NEW piece of furnature every 6 months, therefore, the owners can't get the Big Money Advertisers. They CAN get a car dealership to pay 2 grand a month for advertising, but "Joe's Tatto Parlor" can't afford 2 grand a month for advertising. Now look at it from the Car Dealerships point of view. They are not gonna spend money to advertise on a Heavy Metal radio station because they think the same way. "Heavy Metal" people are not going to by any of my cars.
The other problem is that the stations are owned by corp.'s that have to pay lots of payroll, forcing each of these stations to produce income ten times more than needed to keep a mom and pop station alive. It's a monopoly and there is nothing you can do about it, unless you can pursued mom and pop to keep their station(s) or at least sell them to someone who won't sell out to the "Mighty Dollar".
Not all is lost though. You would be surprised how many radio station licenses are available these days. Many more than ten years ago. The Big monopoly Radio companies are squeezing out the little guys because they can. Fortunately for you, this leaves little radio licenses all over the place in case you decided to re-start a station in your area and try to gradually pick up your fellow musical taste listeners and eventually make a comfortable living, but it would be slow at first. However, eventually, the people will come because you are playing what they want to hear. Then all you would have to hope for is the FCC allowing you to kick the power up now and then to gradually reach your listeners from far away. I agree with strat78. If you are brave enough to take the risk and start one of these stations or buy one that's still running, you can keep the tunes pumping and still make a comfortable living. Unfortunately, greed can sometimes out-weigh your love for the music
