Why do women in polygamist marriages believe it's what God wants?

I've never understood why a polygamist woman really believes God wants them to learn to cope with the jelousy and lifestyle of a husband who couldn't settle just for her? I'd like to think that God loves all his children, even his daughters enough to have one special man, and ONE special woman to share their lives together. Me being married conservatively in a Christian lifestyle has made me very happy, especially to know that I"m the only one my husband goes to bed with, and he's my only man. We are expecting our third child and I love the idea that they're only MY kids and no one else's, why would a woman willingly choose the polygamist lifestyle. If it has to do with 50% of marriages fail, the polygamist marriages are involved in that percentage as well, and about %30 of those marriages aren't Christian.