It's interesting that the all-news stations that had been CBS-owned eliminated the tone at :30 past the hour years ago. I suppose WCBS and other stations figured it didn't want to force the anchors to back-time twice per hour to meet a tone. The top-of-the-hour tone is part of the network news, so that one is still there. The anchors must back-time to meet that tone.
At one time, WCBS used four tones at the top of the hour, three soft and the final tone louder, to help you set your clocks or watches. A few times per day, there was even a message with a deep voice telling us "Set your clock to WCBS. Four tones will follow. The final loudest tone marks the exact time. gong, gong, gong, GONG." I think that got eliminated back in the 1980s. The four-gong, top of the hour tone was gone, along with the :30 single tone. And in reality, the tones today on KYW, WINS and WCBS are not exact, due to the time lag for HD Radio.
Westinghouse-owned KYW and WINS kept their :30 tone. They were not owned by CBS until the 1990s, so they didn't eliminate the :30 tones along with the other CBS all-news stations.
How about the other former Westinghouse all-news station, WBZ Boston? It's not quite the same, since it only went all-news in the early 2000s, not back in the 1960s like WINS, KYW and KFWB Los Angeles. WBZ has a top of the hour tone but the anchors often ignore it. If they meet it, great. If not, no big deal. They might be finishing the end-of-the-hour weather and the tone sounds while they are still reading the forecast. They simply finish the weather and hit the sounder to introduce the new hour when they're ready. I'm not sure if WBZ kept or eliminated the :30 tone.