Why do people say that they hate thier parents ?

Your mom gave birth 2 u, and both of your parents are trying to provide 4 u, like buy you clothes, and provide shelter 4 you. I don't get it !! I mean that girl Audrey from My Super Sweet Sixteen, he mom bought her her dream car, but not on the right day. im all like WTF?! And when like a teenager for e.g gets an "ugly" shirt that her mom/dad got for her or somethin' they are all like " UGH! THIS IS UGLY! I HATE YOU!!!!!!!!!!!!!!'' WTF?! i don't understand.... I <3333 my parents. there awesome :DDD