Joseph Smith, the translator, received specific instruction from the Lord: (1) He was told to “Touch not the things which are sealed” and (2) when he had finished translating what he was permitted to see and had obtained the promised witnesses who would testify of the book, the Prophet was to seal up and hide the record for a future day when the Lord would reveal the balance of the engravings. In fact, the plates were delivered back into the custody of the angel Moroni until that future day (Joseph Smith–History 1:60).
One purpose for having the sealed portion remain untouched, said the Lord, was to show the world that he is able to do his own work, to reveal the sealed portion in his own way, and that he is a God of miracles. We know enough to appreciate that the Lord’s ways are not our ways and that he is fully in charge.