Because everything interesting is in television is available on the internet, that's why. Case and point: Dr. Horrible's Sing-Along Blog. This is a 42 minute long miniseries written by Joss Whedon, who wrote Firefly (which ended with the enjoyable sci-fi action flick, Serenity), and Buffy the Vampire Slayer (which I've never seen, but I've heard is pretty clever).
Dr. Horrible is one of the most original and enjoyable things I've seen. Funny, and surprisingly touching (very surprisingly), it stars Doogie Howser (Neil Patrick Harris/Dr. Horrible) and that guy from Firefly and Waitress (Nathan Fillion), and that girl from Buffy the Vampire Slayer (Felicia Day). And it’s a musical!
Now, my brother and I own a TV. It's very small and fits nicely in the closet where it's been for the past year or so. And we have cable, mainly because of some promotion that made our internet cheaper when we signed up for cable. But I don't really need them. I've got my high speed cable internet (well, when it's working) and my Netflix account, and when absolutely necessary I can go to my friend's house and watch his HD TV. Hulu.com has many of the shows I enjoy with "limited commercial interruption" immediately available (currently watching somewhat regularly: The Colbert Report and Burn Notice).
And with original, entertaining stuff like Dr. Horrible's Sing-Along Blog out there, why bother even plugging in the TV?