This is something I always wondered about because I don't have the answer so, hopefully someone can fill in the blanks.
When exactly did some of the NY Metro Area stations decide to go to all-night programming and was this a decision by some of the stations at the same time? What, if anything, was it in response to and was it a case of "follow the leader"?
The only thing I really have to go by is my collection of old TV Guides but there are too many blanks to come up with a definitive answer. I know that throughout probably the majority of the 1970's, NY area stations signed off the air at certain times. Some earlier then others. I know that WCBS-TV was the one station that stayed on the air the latest, sometimes signing off for a ridiculous 10 minutes before signing on again. Now, I fast forward to my TV Guides from 1981, I don't have any Guides from 1979 or 1980, and lo and behold some of the NY area stations are going 24 hours a day, 7 days a week. Now, what I find most interesting is that the "some" involved two NY local independents. WOR-TV Channel 9 and WPIX-TV Channel 11. The reason I find it interesting is because it's two local indies leading the way as opposed to the local network affiliates. Now, by the time WOR and WPIX began going 24-7, the other stations were staying on later than before but still signing off for anywhere between a few minutes and a few hours each day. This is most interesting to me because I assume before long, everyone else followed suit. I guess this was also the beginning of 9 ALL NIGHT but I don't know for sure. Anyway, looking at the programming for 9 and 11, they certainly had enough to carry them 24-7. WOR threw movies by the bundle at it's viewer while WPIX ran some classic shows such as THE FBI, THE ROOKIES, TWILIGHT ZONE, etc..
My guess has always been that this was in response to some fledgling 24-7 cable nets as more and more folks became wired but I don't know for sure. It's a topic that fascinates me but I'd sure like to have some concrete answers so please feel free to chime in.