Then simply answer this question, BC.
Why do you think the Church didn't make any type of mention regarding Joseph Smith's plural marriages on the official Church website dealing with autobiographical information on Joseph Smith?
If true (because there are references to many materials on that site which may mention it), I'd say because plural marriage is not practiced today and therefore it detracts from the message and is not relevant.
Plural Marriage was a pretty large part of Joseph Smith's legacy. Shouldn't it at least be mentioned? Particularly in reference to his family tree?
Should? Not really. The overall Restoration is far more important than the esoteric doctrines. However, I have no problem answering the question "Did Joseph Smith practice plural marriage?" forthrightly when it comes up. Yes, I am pulling the milk before meat principle on you and why not? Consider: How many lay Christians know that God authorized plural marriage in the Bible? Not many.....