The Phoenix metro area is one of the fastest growing areas of the United States. Why isn't the radio dial reflecting that? You would think Phoenix is some small town radio market judging by its stations. Is there really a need for TWO country stations, TWO FM stations that don't even play music as well as FOUR Top 40 stations? Why aren't any of these corporations implementing new formats since the metro is getting more diversified? What about an Urban AC format? Rhythmic CHR or even Smooth Jazz? Phoenix isn't a small town, it is a big city. Why doesn't it have big city radio?
Phoenix has a 5% African American population. Urban AC has been done in the past on an AM and a rimshot FM. It earned a 0.8 share at best.
Back in the 1990's, which was the last time Urban AC was tried in the market, it was a 2% African American population. That's not enough growth to change the outcome of attempting the format, which is failure.
The only way you can make Urban AC work in this town is if you have a signal that you don't have any other viable format options for and you have other stations in the group that subsidize the operation. EZ Communications and Sundance made Kiss 1230 work because its other stations in the building paid the rent on the studios and paid the light bill, so the station's only real expenses were me (a college student at the time working really cheap), two sales people, and the transmitter site electric bill (1kW AM, cheap). Down the street, Majic 107 tried to make a go of it with a full staff and no other stations to bring in revenue. It was sink or swim and they sank. Phoenix isn't Houston or Atlanta - the billing just isn't there for an Urban format. There's a reason Radio One has never tried to enter the market.
The only ethnic formats that work in Phoenix are those that appeal to Hispanics, because that's who lives in the metro.
KYOT was at one time a huge Smooth Jazz station in the 1990s. Like all Smooth Jazz stations around the country, the format died. It moved to a Rhythmic AC format in 2011 and floundered. It took on its current Variety Hits format in 2014 and now performs well.
As for Rhythmic CHR, KKFR still reports as Rhythmic, as does KNRJ. KZZP and KZON have flirted with Rhythmic in the past, but the musical trends have shifted them back to mainstream over the years.
But to answer your question as to why stations program what they program: they do what makes them money. And while the city is growing, the demographics are staying more or less the same; a low African American population, a good sized Hispanic population, and a majority white population. Radio reflects this: stations either target the white audience, the Hispanic audience, or they build a coalition of whites and Hispanics. Everyone else is just along for the ride. Because that's who lives in Phoenix.
Sure, you could flip any of the stations in the market to Urban AC or Smooth Jazz tomorrow if you wanted to. It would be financial suicide, which is why people don't do things like that. You will make more money as the fourth country station than you will being the first of either of those formats.