Why do women have periods? This sparked up cause there was an advertisement on TV about seasonale, which if taken cuts a womans periods to 4 a yr. First off, why do women have them, whats the purpose and significance? And if its natural, why would you want to mess with your natural cycle to take a pill to cut it down to 4x a yr? This isnt so much just for my knowledge but for knowledge of all men to understand why a woman has one and the purpose of it. Educate us ladies.