I know they are classified as "adult hits," but KKHH's playlist resembles the classic hits stations a la KRTH, KOLA, and KOOL, sound/decade wise. Considering that nearby markets like Bryan-College Station, Beaumont-Port Arthur, Lake Charles, etc. have 70s/80s-centric classic hits, it's kind of surprising the direction KKHH is taking, and even with other Texas markets like Dallas-Fort Worth insisting on having their classic hits being 70s/80s-centric. The outlying areas seem to be similar (or at least not wildly different) to the adjacent markets of Houston. Plus, I've been told that the median age for non-Hispanic whites in the Houston area is high.
Also, WCBS, WLS, WOGL, and WROR in New York, Chicago, Philadelphia, and Boston (respectively) still play 70s music. The former two are especially more similar to Houston as they are ethnically diverse metros. But these are some of the major metro areas that still have a significant amount of 70s in their respective classic hits playlists. And KGLK/KHPT has high ratings, and I believe they are still playing the 70s.