Simple answer: They give options.
None of those shows are my cup of tea, but CC likes to have dedicated replay streams for some of their higher-profile personalities and shows. So, if you want to listen to AT40 or Delilah anytime you want, there is that option. And you can always listen to Shelly Wade on the Z100 stream live at 4AM.
I only listen to a handful of streams on IHR (like KCRW, WDAS-AM and a few others), but I know that the other streams have their own distinct audiences.