Seems to be the trend with those old cable channels.
MTV played music when I was a kid, but by the time I was in high school the music videos were all relegated to a couple of small programming blocks, often late in the evening, while everything else was mostly Real World and spring break beach house crap, or Beavis and Butthead (which I did not mind). By the time I was in college, music videos were pretty much only found on TRL, in which they were heavily truncated and hardly the point of the show. I always thought Carson Daly sounded goofy on TRL talking about "That's the 3rd most popular video this week..." Really? On what? Certainly not on MTV, because you don't play videos. Where are people seeing these music videos and ranking them? So the company launched M2, or MTV2 (I forget how it was branded at the time), which played music videos 24/7 and got back to what MTV was originally supposed to be. My college roommate and I loved it, along with a channel that had also come along about the same time called Much Music.
After college I didn't get MTV2 for a long time, and by the time I did have it again, I found it was also taken over by a bunch of bullcrap that was not music videos.
Same thing happened to VH1 as well.
It's not so much that I mourn the absence of music videos, because I mostly don't care about new artists/bands or their videos, if they bother to do them. What I mourn is that there is apparently a market for the absolute crap tv that lives on the channels which used to play music videos. In 2009 when Michael Jackson died a bunch of high school girls from my hometown were complaining on facebook about how MTV had suspended regular programming and was playing his music videos all day and talking about him. They were incensed that some bullshit apparently called "16 and pregnant" was being bumped in favor of "talking about someone nobody remembers or cares about." I had to look up what they were even talking about, and when I saw it was a reality show about exactly what it sounds like, I realized I didn't care if their older siblings or parents were my friends or if they knew me from church or whatever....they were idiots and they all got unfriended.
I never watched much CMT, but I believe the same thing happened to that too.