You are not obsessed with celebrities because you are a star-struck Hollywood junkie -- it is because of evolution.
That is the theory of an anthropologist at Durham University named Jamie Tehrani.
He wrote that unlike other primates who only respect physical dominance, humans choose to respect certain people if they see that they are good at something. Over the course of thousands of years, that emulation allowed the expansion of intelligence, not just strength.
For example, if someone was good at making a stone knife, they were likely good at other useful things.
With celebrities, we perceive them to be more important that other people because they are successful at something, so our brains think we should respect them, look like them, dress like them, etc.
According to Tehrani, reading tabloids and following celebrities is like junk food for your mind -- it is quick, easy and satisfying, but not necessarily good for you.