They're going to keep adding new stuff to keep chasing the younger demographic.
https://fivethirtyeight.com/features/why-classic-rock-isnt-what-it-used-to-be/
The stations find a cluster of people who like the music that makes up the core of classic rock, and then finds out what else they like. They like R.E.M.? Well, R.E.M. is now classic rock.
https://fivethirtyeight.com/features/why-classic-rock-isnt-what-it-used-to-be/