I would speculate that polygamy was one of the things God tolerated in His Saints, but did not necessarily condone. I believe that God's original design for the institution of marriage was when He made Eve for Adam. Never is there mentioned more than one wife for Adam, nor did he have a special friend named Steve. Eve was made as a helpmeet for Adam. To complete him, and be his companion. Adam loved Eve, because she was part of him, and created to be his companion and helper, and was literally of his flesh. God didn't make him more than one wife.

There is precedent for God tolerating things but not condoning them in the Bible. In the case of divorce.

Matthew 19:8 He saith unto them, Moses because of the hardness of your hearts suffered you to put away your wives: but from the beginning it was not so.

Notice the last 8 words of the verse. Divorce was not part of God's plan for us, but it was tolerated.