Why not? Do you think that in order for a family to be labeled as a "functional family" they are required to spend every waking moment together? Now, we all know that reality does not work that way. teenagers spend large amounts of their time in their own room, doing whatever they like doing. Or they spend time with their friends. and that's considered perfectly normal. And yes, spouses often have different interests that they like doing. And there's nothing wrong with that.
Why is it OK for a kid to go read comics in his own room? Or a book? Or listen to some music in his own room? But if he instead decides to watch a movie on his Mac/iPod it suddenly means that the family is "dysfunctional"? Yes, each member of the family might be watching their own movie on their own screen. So? Each member of the family might also be reading their own book, or reading their own magazine, yet no-one would start labeling them as "dysfunctional". Yes, they would be doing the same thing (reading/watching a movie etc.), but that doesn't mean that the action could be shared. Like I said, one member of the family might enjoy a movie that others do not, should they still share the experience of watching that movie?
Thinking that family is "dysfunctional" because of things like that is way too simplistic