This is due to location: You don’t have any stations which focus on classic rock, but instead Adult Album Alternative (AAA) stations, which are broader and, therefore, can draw a larger audience. This is common in smaller markets, where you need a larger portion of the total potential audience to justify existing at all.
Yes, but not one which will be reflected on AAA stations: Rap, punk, and disco all came into the mainstream in that era, but AAA stations studiously ignore this, focusing instead on the future development of guitar-oriented traditional rock music to the exclusion of all else, until punk was calmed down a bit and branded as New Wave for MTV. Why? AAA is straight White person radio, and, apparently, straight White people would rather hear Creedence Clearwater Revival than The Sugarhill Gang or Richard Hell and the Voidoids.
What else has happened was the death of Oldies stations, which were stations which focused on pre-Beatles rock and roll, instead of picking up the thread around the British Invasion and focusing on psychedelia, singer/songwriter, and Southern rock. Oldies stations played more pop-folk (Kingston Trio), doo-wop, and teen idol music like Bobby Vee, plus, of course, giants like Chuck Berry, Fats Domino, and Elvis. That music is largely gone from terrestrial radio for the simple fact the biggest demographic for it is too old and dead to bother with.
During the late 1960s and much of the 1970s at least, that was a fair description. But once Album Rock became late 1960s and later, without the pop/bubblegum from the immediate post-British invasion era, at least IME the oldies stations picked that up. They’d be where you’d hear the Grass Roots or the Young Rascals. I think you’re right that the pre-Beatles stuff still dominated the format, though.