I am jumping the gun on my normal schedule and writing something I had no intention of writing until a few minutes ago in order to post this today. I just feel impressed to do so.
I believe that the major reason polygamy was revealed, taught and practiced by Joseph Smith was to solidify the foundation concept of eternal families early in the Church's history. Almost everything Joseph Smith taught focused on and developed our current understanding of eternal life and eternal marriage - and the universal application of the Atonement that provides the possibility for all to be joined (sealed) as part of a great, heavenly family. It is perhaps the single most unique aspect of the restored - that we can be sealed to our spouse for time and all eternity - that family ties can last forever through the power of the , embodied in a marriage ceremony and embedded in an ever-expanding family of equals.
Part of why I have not struggled personally to accept polygamy is that I have read journals written by my (and my wife's) ancestors and others who practiced it - journals that are full of both struggle to accept it and great manifestations of God to them as they did so. Some of the most powerful things I have read were recored in response to their own "furnace of affliction" that was polygamy. These journals also gave me a concept of what they envisioned by its practice - the embedding of the concept of universal, familial, communal sealing of a people (the symbolic tying of all into one large family of God and body of Christ) that we have a hard time understanding in our own modern, monogamous society.
It is conceivable that a group of people could believe in the concept of eternal marriage that includes ties beyond just a marriage and immediate family without practicing it here on earth, but the practice of polygamy and the persecution that followed embedded the concept of eternal family deeply into the souls of the earliest members in a way that could not have happened by listening to a Sunday School lesson or General Conference talk. They lived it and were persecuted and killed for it, so they KNEW it - painfully and deeply and undeniably. It literally was carved into their souls.
Having grown up in a small, Utah town where I was related in easily traceable ways to at least 20% of the town, I also got a taste of this communal sealing - and it can be powerful in practical ways. That over-arching concept of literal, expansive and all-encompassing FAMILY that makes all of us brothers and sisters is one of the beauties of Mormon theology to me. I don't think it could have been engraved in our cosmology without polygamy in quite the same way - just as I will never understand a nicotine addiction quite like someone who has smoked heavily and then quit. I'm glad I can't understand either through personal experience, but I'm grateful for those from whom I have learned polygamy's symbolic power vicariously.