Well, I'm glad this turned into a discussion.
But the appeal of watching someone live in a perfect world is also entertainment because it gives us a diversion from our imperfect world. Is that what you mean?
Yes, it makes us forget about who we are and lets us live as someone we would like to be. I don't know whether that's good or bad. The positive side of it is that you can find inspiration, it gives you a vivid example of what you would like to be. Like, for instance, some of MTV's I Want to be Made can show how a regular person can become something he always wanted to be. The negative side is that you become dependant on those characters, you live life through them rather than living your own, and waste yourself in the process. You settle upon something illusionary and unrealistic, it's a drug that separates you from your OWN desires, unless that is a person's desire, to watch other people live.
Perhaps we are living, just not living consciously most of the time, but I doubt there is a nefarious reason behind it. While Carrey's character may have been living in the moment, his world was a falsely constructed one, perhaps that is the ultimate fear that you are hinting to? Or are you merely talking about having a greater sense of urgency or purpose?
Of the two, I'm probably more inclined to agree with the latter. I don't know if anyone felt like this, but have you ever felt like you wanted to do something so much, like ask a girl out or win at your favorite sport, and there was something stopping you, like your reality that you imagine it to be cannot be realized because there is something in the way? In the movie, there were weird circumstances that stopped him from getting out of his idealistic world. Well, the director guy even said that if Truman really badly wanted to, he could escape and there is nothing that could stop him. However, he had to conquer his biggest fears in order to escape. Well, i think life is the same way, you must face your fears and let go of uncertainty (matrix idea), only then will your desires become reality. People, instead of doing what they really want to do, construct a false world themselves full of illusions that only divert them. I'm not trying to say that to live in an imaginaryy world is bad, I mean that it is bad to not know and confuse the two worlds. I'm trying to say is that we should strive to make our imaginary world reality, not to replace reality with an imaginary world.