Why do you think girls are so passive aggressive?

I'm a girl with a very assertive personality. I'm very honest and I don't talk in circles, I get to the point. Yet, I notice almost all of the other girls I've come into contact with are terribly passive aggressive which couldn't be more annoying. I don't notice this with guys though, or mature, successful women, so I want to know, what makes girls and unsuccessful women so passive aggressive? I'm looking for opinions from girls, but guys opinions are welcome too! Thank you in adavce!
Why do you think girls are so passive aggressive?
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