"Integrity has no need of rules." -Albert Camus
We don't know everything about the Plan of Salvation nor do we fully understand God's designs for mankind beyond the general "might find joy."
Each dispensation has had it's rules, leaders, cultures, laws, and enemies. No two were ever the same. From Adam VS Egypt to Helamon VS the Soviet Empire each has had different challenges to face and each has handled them accordingly. To find a common thread connecting these many peoples you don't have to look far. Love thy neighbor, thou shalt not kill, chastity; the Laws of God are clear, eternal, and unavoidable.
Rules and errata are left to the people. I have no idea how important it was to only walk a few steps on the Sabbath but that was the rule for an entire civilization. That rule got changed (voided, really) but not until the start of the following dispensation. Obedience to the rule was, in fact, a condition of continuing in God's good graces.*
Or was it? Could a man of a previous dispensation have doubted the rules and sought out the higher laws? What would that man be in the eyes of his contemporaries? A heathen, a heretic, a Samaritan?
Even now, in the Dispensation of the Fullness of Times, we haven't learned everything. Until such knowledge is gained the modern Church works policy based off the best understanding available. This knowledge comes from sources both temporal and divine. It can be painful to witness and even worse to bear.
Just ask Jane Elizabeth Manning James.
She was an early pioneer of the church. Black and female she served the Smith family after her baptism in 1842. Following the death of Joseph she was taken in as a servant by Brigham Young. In the years preceding her death she petitioned church leaders to allow her to be sealed to the Smith family claiming she was asked to by Emma to do so prior to the events at Carthage.
Early in 1894 she received word that her petition would be granted. Arriving at the temple she was informed that she would not be allowed entry but would instead be sealed, by proxy, to "be attached as a Servitor for eternity to the prophet Joseph Smith and in this capacity be connected with his family and be obedient to him in all things in the Lord as a faithful Servitor."
This is the only known occurrence of a sealing between master and servant. That was what the rules called for but was that what God really wanted? Was that really ever in the rules?
It took nearly a century for the church to figure out the problems with that and it may take another hundred to figure us out.
That's fine. The church can move at it's own pace. I'm not going to agonize as to why it hasn't happened yet. I don't know why President Hinckley answers questions about homosexuality with, "I don't know." He'll ask eventually. If not then a future prophet will.
*Regardless of the motive and regardless of who wrote the rule.