What is the difference between a married man who has three mistresses,and a man who has three wives?

Lets not ignore that men pledge to love their wives till death.Then they go ahead and keep the wife,but will have a couple of side jobs.This we all know.Why ,then,not go through the vow of sanctity and marry three wives?Or does the Law interfere so much in relationships that we end up keeping the law but ignore humanity,love,relationships,and all that?I would like to marry three wives,there are these three women that am in love with,they all love me,they know each other........BUT the Law steps into my life and i wont be "allowed" to marry all three of them!!!! Why,Why,Why.....