Well im not obsessed with celebrities like Britney Spears or Justin Bieber (really any mainstream celebrity i do not like)I am obsessed with Blessthefall though:) i love them dearly!!! I would say i obsess about them because i love them and who they are as real people:)
I think the reason why people have celebrity worship syndrome for people like Britney spears and Justin Bieber is to compensate their dull life. Another reason could be how the media has over hyped and sensationalized celebrities. Check out the link for more information http://en.wikipedia.org/wiki/Celebrity_Worship_Syndrome.
Because their parents didn't teach them to value and appreciate more important people in our lives. My 5 year old daughter can name several Medal of Honor Recipients, but has never heard of this Justin Beiber person of which you speak. She does know who Joan Jett is though, and loves her music, but she doesn't worship her.