Is there so much music repetition during weekdays when people are listening at work?
I don't recall Z100 ever marketing itself as an "at work station." That's WLTW. The OTHER iHeart station in NY.
One of the hallmarks of the CHR format is repetition. Take a small playlist and play the currents every two or three hours. That's how hits are made. If a song can't hold up to that kind of airplay, it's not a hit. It worked for WABC in the 60s and it still works now. You call it "sanitized," but the radio word for is it "curated." When most people make their own streaming playlists, they look exactly like the Z-100 playlists: A small group of songs played over and over.