A few weeks ago I read an article written about a particular show that I watch. Basically the author was pointing out about how in real life, stuff that happens in the show wouldn't happen in real life. I won't go into detail because it doesn't matter.
We instinctively want to get outside of our own lives and see something different, exciting, not us. It's the same as reading fiction books. We don't read to learn about human nature. We read to escape into a different world, a different life.
That's not to say that we want a TV show to be totally unrealistic. Just sort of unrealistic. Enough unrealistic elements to make the show entertaining but not far-fetched. If you want a totally far-fetched show watch the sci-fi channel. For most of us (in my opinion), we just want an escape from the hum-drum regularity of our lives. We want someone else' life for the space of 30 to 60 minutes. And then we can come back to reality.
As I told the author of this article in my comment (in a kind way, mind you) if I wanted realistic, I'd watch the news.