"Wow, that was a real moment. That's weird for MTV."
Joel McHale: Hey, ya know what else is weird for MTV? Showing a music video.
— The Soup
One of the most documented cases is that of MTV, which began in 1981 as an all-Music Video station. Now it only plays music videos in the early morning hours of weekdays — the rest of the time is devoted to original non-music programming, mostly teen dramas, talk shows, and reality shows that have nothing to do with music (or often, for that matter, reality). That, or programs from other Viacom-owned networks, such as American Gladiators and even SpongeBob SquarePants.
The decay began in 1987 with Remote Control and continued in throughout the 1990s with The Real World and Beavis and Butt-Head
(the latter of which featured music videos, albeit with MST3K-style commentary by the title characters), two of the most popular programs in the network's history. The MTV executives saw this and started commissioning more non-music shows, until music had been pushed into late night/early morning and the after-school Total Request Live (TRL) block. At one point, they even ran commercials with the tagline "MTV: We Don't Play Music." Since the cancellation of TRL in 2008, the only lip service it still pays to its roots is with the "AMTV" blocks of videos. In 2010, MTV's logo was changed◊ to omit the words "Music Television".
Beavis and Butt-Head could be an indicator of how it decayed. It started off as about two minutes of animation and the rest was music videos. Then, the animations got longer as the videos became much more expensive to license. Then for a while, during the bottom of the decay they had nothing in between animations. A short-lived relaunch in 2011 was closer to the original, albeit with MTV shows as well as videos.
In some European countries, MTV still primarily shows music videos. American reality TV isn't nearly as popular outside America. That also used to be true for Latin American MTV, but it eventually followed the steps of the U.S. channel.
In the United Kingdom, MTV UK was re-branded as MTV One (now just plain MTV) and shows nothing but reality shows, animation, and live-action scripted shows such as Pretty Little Liars and Blue Mountain State. note MTV UK's genre channels (MTV Base plays Urban, MTV Rocks plays indie rock and alternative, to give two examples) have their own programming related to the music they play, such as interviews. These have been cut back in favour of playing more music videos, leading to perhaps the first known instance of MTV being criticised for playing too many music videos. In 2011, MTV UK more or less stopped pretending to be a music channel, moving alongside the entertainment channels on Sky's EPG and launching a new channel called MTV Music to fill in the missing gap.
The French and Walloon (southern Belgium) MTV used to be an English-language channel (weirdly enough). They added subtitles and later dubbing to some of their shows (mostly animated shows and live broadcasts) before adding original French-language shows. This only made sense, considering the market, and they still aired plenty of music videos. However, like its foreign equivalents, it drifted toward reality shows (both original French shows and imported ones). It still airs some music (predominantly hip hop), but late at night.
At one time, there were three music channels in the Netherlands — MTV, The Music Factory (TMF), and The Box. MTV followed the all too familiar pattern with programming first shifting into the mainly R&B/Hip Hop/Rap genre, eventually phasing out to "reality" TV (although nothing Dutch; just stuff from the U.S.). TMF, the first true Dutch music channel, was soon bought out by MTV's parent company and changed from a channel with VJ's and life shows to a SMS-your-thoughts channel in addition to a radical music style change.
The Italian MTV is also taking this route. Until the late 1990s/early 2000s, most of the schedule was composed of blocks of music videos and the occasional anime or South Park episode. Now it airs at least five or six episodes of American reality shows every day, and only two blocks of music — one early in the morning and one late at night. There still is the occasional horror movie or anime, but those can be found only after midnight and change timeslots frequently.
In Australia, pay TV company Foxtel, who has channel numbers ordered by categories, acknowledged this in November 2009, when they moved MTV from channel 808 (8xx being Music Channels) to 124 (1xx being General Entertainment Channels).
New Zealand had C4, which was essentially MTV, up until the first quarter of 2011 when the channel as it was being renamed to 'Four' and another channel being set up to play music videos full-on (now called C4 in the old channel's stead). It remains to be seen whether the cycle will repeat.
This trope is enforced by law for MTV Canada, whose broadcast license heavily restricts the amount of music-oriented programming it can air, and has Canadian content obligations during certain daypart. However, this was because of its own Total Abandonment; before becoming MTV, it was talktv, a network dedicated solely to talk shows (mostly re-ran from CTV). Since the license was not changed, MTV Canada slipped right out of the gate.
In the 90s and early 2000s, MTV Brazil started moving towards variety shows (some had relation to music, such as a soccer tournament between musicians and a movie show that showed videos for songs popularized in soundtracks). Then in 2006 they decided to pull the plug on their TRL equivalent, marking the point where the decay became irreversible - even if music countdowns and such are still featured (though not as popular\prominent as the comedy and tween-focused shows). Then the "original" MTV, with broadcast signal and owned by a media conglomerate under the license of Viacom, was closed and the new cable channel under Viacom command is still barely about music.