It's because I'm married, and my TV time is not my own.
Sure, I work at home, and I've got the entertainment center to myself most days (except when my kids are out of school and watching Blue's Clues or asking me to actually, you know, play a game with them or read to them or something). But daytime is primarily worktime. At night, after the kids go to bed, my wife and I grab our respective spots on the sectional–her in the crook, me on the end with the recliner–and we watch about three hours of TiVo-ed TV, typically while catching up on web-surfing and e-mail. And if there's a sporting event of significance on, we usually have it in the corner of the screen, PIP-style.
Because our attention is usually divided, the TV genres that play best in our house are sitcoms, reality shows, and dialogue-driven dramas like Gilmore Girls and Veronica Mars. In general, my wife isn't as big on action/adventure or sci-fi/fantasy, because it requires too much concentration. (The exceptions being Lost and The Shield, which she's already hooked on; and Heroes and The Nine, which have gotten to her early.) I had to watch the first season of Deadwood mostly without her, because she wasn't that enthusiastic in the early going, and even though I told her how great it got by the end, it was too late. (I've still been dragging my feet about picking up the second season set.) I did Firefly on my own too, and most of Life On Mars. But I'm determined to get my wife to share Battlestar Galactica with me, because I can't stand not being able to talk about my favorite TV with my favorite person.
I'm waiting on The Wire too, until we can devote the kind of attention to it that we devote to The Sopranos whenever we get a new DVD set. (We close the computers, turn off the lights, and watch two episodes a night until we get through the season.) Maybe we'll get to it next summer, by which time we may have seasons three and four to watch, too, and we can do a long run through the whole shebang.
How about you, dear readers? What shows (or movies, or music) can't you get your significant others to enjoy, and how does it impact your relationship with pop culture (not to mention your actual relationship)?