I have sat through the same SportsCenter twice (sometimes they repeat it immediately after it concludes) without changing the channel, likely because I was focused enough on whatever I was doing on the computer that I didn't notice it end and begin again. (Interestingly, in those cases, almost invariably I will glance up during the second showing and see the same highlights I did glance up and see during the first showing. It's like I have a cyclical pattern to the moments when I need to look away from the computer screen and engage my attention elsewhere for a few seconds.) I have sat through the same Syd Barrett biography on VH1 Classic that I've seen before for that very reason—I've seen it before; it doesn't require attention.
The worst part is that this was not a habit I developed as a child. I never had a TV in my room while growing up. I spent a lot of time in my room, but I listened to the stereo. The TV was out in the living room, and I only turned it on when I went out there specifically to watch something.
Those were the days.
It wasn't even the case that the habit started when I moved out to my first apartment. There I lived with someone, and while we did watch TV sometimes, it wasn't always on. It wasn't until after we broke up and I moved to my second apartment, living by myself, that I started putting it on just for the sake of having it on. Sometimes I'd mute the volume and have the stereo on at the same time, because I didn't have any interest in whatever program was on, but I didn't want to turn it off. I guess it approximated, in some hideously pathetic way, some contact with others; it staved off being lonely, just a bit.
However, after I moved into another apartment, this one with a roommate (where each of us had a TV in our respective bedrooms), I don't remember doing it as much. I could be in the room with just the stereo on again. And when I later moved in with another girlfriend we spent even less time with the TV on when not really watching.
But then when we split and I was living alone again (again in a studio apartment) I got back into it. And in that apartment, using the computer meant sitting at a desk, where when facing the monitor the TV was behind me, so I could not merely glance up periodically and see the screen; I had to completely turn around. Nonetheless, the TV was on, I suppose just to hear human voices in the room.
Now, I'm engaged and don't spend much time alone. That's not what it achieves for me. So why does the behavior persist?
The stereo doesn't have a remote control like the TV does. If I don't like what's playing, or I need to turn it down because the phone rings, I have to get up. Not that I can't get up—I'm perfectly ambulatory—but I've come to not want that.
So, ultimately, it's lack of convenience.
I'm not sure that is any less pathetic than loneliness, is it?
Homer: Hey Bart, how come you never play your guitar any more?
Bart: I'll tell you the truth, Dad. I wasn't good at it right away, so I quit. I hope you're not mad.
Homer: Son, come here! Of course I'm not mad. If something's hard to do, then it's not worth doing! You just stick that guitar in the closet next to your short-wave radio, your karate outfit and your unicycle, and we'll go inside and watch TV.
Bart: What'll we watch?
Homer: It doesn't matter...
The Simpsons, episode 8F21: "The Otto Show"