God made Adam and Eve, not Adam and Eve and Mary and Cathy and Sally----
It was the original plan to have only one wife.
Gen_2:24 Therefore shall a man leave his father and his mother, and shall cleave unto his wife: and they shall be one flesh.
It's a little hard to be one flesh with more than one wife. It wasn't until Lamech that more than one wife is mentioned.
Gen 4:19 And Lamech took unto him two wives: the name of the one was Adah, and the name of the other Zillah.
Noah had only one wife, so did his sons. Abraham had one, when Sarah had him take the bond woman to have a child it was because she and him both lacked faith---and the heartache of that decision is still being felt today.
Where there was more than one wife, there were problems. The High priest had to marry a virgin and more than one wife was discouraged.
http://www.chabad.org/library/article_cdo/aid/558598/jewish/Does-Jewish-law-forbid-polygamy.htm
A close reading, however, reveals that in virtually all cases where our forefathers took multiple wives, it was for a specific reason. Abraham married Hagar only after Sarah suggested that he do so because she and Abraham had no children together. Another classic example is Jacob. He married Leah only because he was tricked into it by Laban. Similarly, he took Bilhah and Zilpah at the advice of his first two wives, who wished to bear children through them.
Yet the Torah does not outlaw polygamy.
As far as Jewish thought is concerned, it would seem that polygamy is not, and never was, an ideal state. The mystical works are replete with references to husband and wife being two halves of one whole. Interestingly, I’ve never encountered an episode in the Talmud or Midrash—which predate Rabbi Gershom’s ban on polygamy—which involves a polygamous family. While it is certainly possible that such stories do exist, it is quite apparent that polygamy was never the norm.
Practically speaking as well, polygamy is a big financial strain, as the husband is required to provide for all the needs of, as well as separate housing for, two households.
In all probability, polygamy was always considered a last-resort option for men who were married to barren women and who wished to have children without divorcing the wives they loved. Monarchs also routinely used polygamy to cement relationships with different tribal factions and families.