There's a reason why prime time TV is called prime time. Late night TV has usually been for horrible movies, many of which I love of course, re-runs of I Spy, and in later years, infomercials.
I'm not sure exactly when they came in, probably the late eighties, and sure it was funny to watch because a lot of what these guys were pitching was so ridiculous, but I hated it because it took away the B movies I loved that played late night, and soothed you into the pre-dawn hours.
Not to mention, there were late night commercials that were a lot more fun before the dawn of "infotainment," like used car salesman Worthington Ford, who many still love to this day, although we certainly never bought any cars from him.
A lot of this stuff could help you sleep, not just because a lot of late night movies were terrible and could cure any insomniac, but because you got used to these things being on late, and it would almost trigger sleep in your body.
To this day, I love looking up old commercials and late night programming on YouTube, and it's like running my own little network. Late night movie shows, like Movies Till Dawn on Channel 5 in L.A., had a wonderful helicopter shot of L.A. at night, and a great theme that still takes me to a happy place in my head. (I think you can buy it as a ringtone).
The great B movies I love flooded late night TV because the story goes when a major studio sold their big movies to TV like Gone With the Wind, the network had to take a lot of schlock in their libraries as well, which became relegated to two in the morning. This also created the wonderful phenomenon of horror hosts like Vampira, Elvira, who were hired to make fun of the movies, and this later would lead to Mystery Science Theater.
I can't recall exactly when infomercials took over, but the key ones that showed that TV was changing in this direction was Tony Robbins, and Ron Popeil whose company Ronco came up with such incredible innovations as the Veg-O-Matic, Pocket Fisherman, Mr. Microphone, and GLH, or hair in a can as many will call it.
Watching the A&E Biography of Tony Robbins, I found out it was in the late eighties that a new law came in where you weren't limited on how much commercial time you could buy on TV, and then there was infomercials that presented themselves as real TV episodes in a half hour format.
Of course a lot of us didn't take this stuff seriously, and we'd laugh at GLH, The Psychic Friends Network, and Tom Vu, who cruised around in a boat full of bimbos, and had seminars to teach you how to get rich. A typical Vu missive was, "Do you want to make a fortune? Come to my seminar. You don't come to my seminar, you deserve to be broke my friend."
And of course, we knew a lot of this stuff was pure horsesh*t, but this was of course a numbers game. You shovel enough horsesh*t to enough people, somebody's gonna buy it. But again, most people knew this was all nonsense, and we would just laugh at the audacity of these guys. There's certainly no such thing as easy money, or getting rich quick, especially in today's day and age.
I think I knew once I saw the airwaves cluttered with infomercials that there was no turning back to the late night TV I loved. For others that loved old school late night TV, it's also been a terrible loss.
As Michael Weldon, who used to run Psychotronic magazine once told me, "For me, late night TV on local stations was it. If you didn't see something in theaters, you saw it on TV, and I had spent most of my life watching these kinds of movies on late night TV. They were replaced by late night talk shows, repeats of old cop shows like Kojack, and then it got even worse when the infomercials took over. Movies just disappeared. I didn't have cable for years, and TV just died for me. It was like, who needed it anymore?"