I can sense jealousy coming from all directions if somebody is married the person first, and then realizes s/he married another person.
It's like 'sleeping around'. Gotta keep them happy you know. ;]
Too much work, too much stress, too much risk involved.
A wife is married to a man. The husband wants to have another wife. The wife doesn't approve. So the husband files a divorce after asking the other one he wants to marry if they had problems with having several spouses. The 'fiance' doesn't mind. But the ex-wife suffers from heart break and feels as if she was used, as he didn't love her enough to keep her, rather than going off and marrying three different women.
This will in turn arouse a hostile and bitter emotion in the ex-wife, thus creating only more trouble.