It's another one of those things that's fun and appealing as a vague concept, but wouldn't be so great in real life. Trying to keep one partner happy is hard enough, but keeping multiple partners with different needs all happy would be absurdly exhausting, if not downright impossible. Plus it detracts from the overall power you have over your life, if one wife makes you throw away your favorite couch, what exactly do you expect to have control over when you have 7 wives, no thank you. Also, jealousy is cute in a show, it's terrifying in real life.