I tend to agree with Carlotta that TV is given too much of the blame. It makes a convenient scapegoat, that's for sure. We hear people say that TV is the culprit so often, there's a tendency to take it for granted as incontrovertible truth.
But children have so many other sources of amusement that they didn't have when I was growing up. As Cloud says, there were fewer TV shows that were likely to appeal to children back in the day; certainly that was true in the '50s when I was growing up. And no computers, or video games, or iPods, or ... well, the list goes on. With all that time on our hands, you would think my generation would all be voracious readers, but that just is not the case at all.
The kids who lived next door to us, none of them had a love of books, although there were plenty of good children's and YA books in their house -- I know this, because I borrowed a lot of them. And my older brother and sister, they don't read much either; I don't believe that I've ever seen my sister pick up a piece of fiction and read it in my entire life. I have many fond memories of my father reading to me when I was small, so it's more than likely that he read to them, too, when they were little, and naturally they had access to the same books that I did. As for TV, they're both in their sixties now, so you can imagine how much of that they were able to watch at an early age. (I remember the first time I ever saw a TV; it was at a neighbor's house, when I was about 3, which means my older siblings would have been 9 and 11.) I love to read, and they don't. It's hard to see how TV could have been a factor; they simply found other interests, and continued to be interested in those things instead of in books.
In the end, all parents can do is encourage their children to read, and make the books available -- after that it's just a case of individual personalities. To let parents whose children did not pick up the habit in spite of all their encouragement feel that they are to blame -- because they let their children watch too much TV, or whatever reason -- just isn't fair.