In real-life, who can you stare at with impunity/immunity, without feeling weird or having to look away? Only babies and little kids.
Aside from that, we're absolutely starved for being able to watch our fellow human beings. Just as we're starved for being able to have some insight into what strangers are thinking.
Thus the invention and power of the movies. And of blogs. Both enable you to look and look and look, without being judged yourself.