Brooke, 
 
I don't think we know - or may never know on this earth - why the Lord gave this commandment. All we know is that the Lord did command it and the early brethren of the church agreed to do it although it was extremely painful and difficult for them to accept. 
 
We know that there was polygamy in Old Testament times that were commanded and sanctioned by God. 
 
There has been some speculation that some of the reasons for polygamy in Joseph's time were: 
- There were more women in the church than men as a result of the conversion process. (Part of this is that women tend to be more spiritual than men - as a result there were more women than men.) 
- There was a need to produce many more offspring to help grow the church 
- The Lord wanted to test and try the faith and obedience of the early members of the church. Kind of a winnowing process 
 
In any case - I don't know the reason. I know it would be very difficult for me to accept such a commandment. 
 
I suspect that we probably won't know the reason until we are gone to our graves and it is revealed to us later. I also suspect we don't have the same perspective on things here on this earth than the perspective of things in Heaven. 
 
I can guarantee you that the Lord sees women in an equal light as compared to men. I know that the whole purpose of us coming to this earth is to gain a body and prepare ourselves to live again with Heavenly Father. There is no more important role in this process than that role that women play. The nurturing and raising of children is really the most important calling/mission we have here on the earth. 
 
If you want more of a professional or educated point of view - I would refer you to fairlds.org. Specifically you can learn more about the whole area starting here: http://en.fairmormon.org/Polygamy

To start off God never commanded polygamy. You will find no Command in the Bible, Book of Mormon, or the D&C to marry multiple wives.  
 
God has allowed polygamy in the past dispensations and in this dispensation (until the laws of the land banned the practice) to preserve his people and fulfill his will. A plural marriage could only be sealed with the approval of the First Presidency and any current spouse(s).  
 
I do not understand how a man having more than 1 wife means the women are being shared? The Church has never practiced or endorse anything where husband share there wives with anyone.  
 
A marriage is the only place where intimate relations are appropriate so sharing a wife with anyone is grave sin.  
 
Joseph Smith did support the practice he himself had 24 wives though he only had children with Emma.  
 
It is confusing because at times Joseph appears embarrassed about polygamy and never publicly discussed his other wives. Him and Emma deny claims that he had more than one wife all the way to there graves. So there is a lot of confusion here. Rememeber that at these times the practice of polygamy was grounds for most Anti-Mormons to attack and even kill Mormons so a lot of early saints denied there plural marriages in fear of there safety and life.  
 
What we do know 100% is that God has always allowed plural marriage. Plural Marriage has never been a commandment and having mulitple wives is not a requirement for heaven (as many anti-mormons falsely proclaim we teach). 
 
God does call in certain times for chosen men to take multiple wives to ensure there prosperity such was the case of Abraham and to raise a people up. 
 
Most assume that this is the reason of the polygamy in the early Church having reestablished the Church of Christ and with many men killed God had men take multiple wives to ensure the posterity of the latter day saints.  
 
This seems logical and makes scriptural sense but there is no official explanation given in our scriptures. We know that God allowed it in the past and in compliance with the Law of the Land the practice was stopped in 1890.  
 
Thank you for your question Brook and I hope my question helped you!