Do you believe in star signs and why?

I don't, I'll be upfront about it, but I am not asking this to ridicule the belief or anything...I just want to know why there is such a widespread belief in this. My own personal proof of the star signs being incorrect are that my father and my aunt are both Capricorn and they are almost polar opposites in personality. (One is a social light, chatty, hyper, impulsive, the other is careful, a workaholic, responsible, introverted and shy). I am...I think....a Scorpio...and I don't feel like I'm very mysterious or anything, and I certainly don't have any desire for power of any kind. I tend to be a very mild sort of person, my husband is definitely in charge of the relationship, for example. Anyway, I just wanted your thoughts, and I wanted to understand why this belief is so...well...believable when it seems so wrong....(Again, I am NOT attacking anyone, please believe that)