A sad fact of television remains that, no matter what, at the end of the day it's about about earnings over art. So when TV channels change their content completely, you know that someone just sold out. TV channels that started as something different never began with the intention of eventually selling out, but the demand for content like true crime, sci-fi, and reality television proved to be profitable in the end. TV networks that changed their focus, whether they realize it or not, merely reflect the public's shift in interests over the years. Today, people would rather watch Dance Moms than an actual ballet performance, so what exactly did you expect A&E to do?
When it comes to channels that forgot what they're about, TLC emerges as the prime example. How do you go from being The Learning Channel to airing Here Comes Honey Boo-Boo? There's definitely nothing to learn from that show, to put it mildly, except that Mountain Dew should be consumed in small amounts. However, not all TV channels losing their way needs to be seen as a bad thing. Breaking Bad isn't what AMC originally intended to air when it first launched, but it entertains people far more than "classics" like Gone With the Wind. Some of your favorite TV channels started as something completely different than what you know now.
What They Show
Mostly reality shows. Stuff like Trading Spaces and Junkyard Wars justify their existence on The Learning Channel by being slightly more documentary in nature than most reality shows. These shows focus more on the stuff that they find in junkyards and... whatever-the-hell-it-is-Trading-Spaces-is-about, instead of answering more standard reality show questions, like, "Who can eat the most worms?" and "Who can flip the most tables?"
Some of the younger folks out there in Internet Land may not realize this, but The Learning Channel once cared about learning – like, in the academic sense. Blocks such as "Ready Set Learn" and "Cable in the Classroom" pioneered the medium of television's potential as a teaching aid.
Obviously, this failed catch to on (or make a profit for investors), likely because people watch not for information but for incendiary content. After the nonprofit organization that owned TLC went bankrupt in 1991, the Discovery Channel snatched them up and started slowly pushing them towards less informative, more sensationalist content.
In 2006, they finally dropped their revisionist "Life Unscripted" tagline and (to make reality TV sound cool) replaced it with "Live and Learn," still desperately implying that a) the "L" in TLC stands for "Life" and b) that the channel has anything at all to teach you.
What They Show
Pretty much anything they want. We wouldn't complain if they were just stretching their boundaries ("classic," in the context of AMC, apparently describes Little Nicky and Jurassic Park 3), but at this point, the majority of their most popular programming isn't even movies. You turn on the channel expecting some classic film-stuff, and instead you get TV Shows like Breaking Bad and Mad Men, which are… well, also fantastic. No one's complaining here, just nitpicking.
Back in 1987, AMC's M.O. was to show classic movies, mainly from the Golden Age of Hollywood (1950s and back) without any commercials, content edits, or any form or artistic adulteration. It was an attempt to preserve the magic of a bygone era, or give the grandparents something to do while you smoked pot in their basement, or something.
It's unclear what exactly accounted for the shift, but in the late '90s, AMC started showing much more recent "classics" such Unforgiven and Thelma & Louise and Speed and Unforgiven again, because holy crap do they like movies.
The increasing competition from TCM (Turner Classic Movies) may explain the shift in programming, but no one cares because people enjoy Breaking Bad more than Golden Age Hollywood anyway.
What They Show
Somewhere in the mid '00s, MTV decided to march to the beat of their own drum, specifically by avoiding beats and music altogether in favor of reality television. MTV not only cornered the market on stupidity – they've patented it, packaged it, slapped in on a plastic lunch box and now bam! – you're watching a bunch of tan people who may-or-may-not be Italian act like like stereotypical guidos in New Jersey.
The Internet, specifically services like YouTube. Nowadays, any music video itch you have can be scratched with your computer or smart-phone. It's little wonder they dropped the word "music" from their logo in 2010 - Music Television was a good idea while it lasted, but that niche just doesn't exist anymore.
What They Show:
Ax Men, Ice Road Truckers, Deadliest Catch, Top Gear, Pawn Stars, and Ancient Aliens. Connecting each of these shows to the concept of "history" requires some mental gymnastics, but in a way, it's simple. The network plays the shows as the action unfolds, thus things happen. Therefore, after time passes, the shows will themselves become history, so "history" is actually a pretty accurate in a non-linear, wibbley-wobbly Doctor Who sense of the word.
At some point known as the "Hitler Channel" because of its obsession with World War II, THC became more focused on reality TV for the same reason every other channel did: it's super freaking cheap. Reality TV is currently the height of Executive Producer Generated Content, in that it requires the absolute bare minimum creative contribution. You don't need actors, or any kind of research to make a reality TV show; you just need to combine buzzwords into titles that are almost puns. Alaskan Bush People? Put it in development!
Sure, you still need writers, directors, editors, and various audio and lighting professionals on the set of every reality show, but you can bet your a** as soon as studios figure out a way, they'll make their jobs history too.