This was a question I had years ago. I prayed, fasted, and pondered about this and other things that were causing me to question the administration of The Church. Now I know the answer. Receiving this answer required prayer, pondering, humility, and fasting. As you search for and receive this answer for yourself you will likely receive answers for other church policies that could be questionable to the understanding of our natural mind.
It would be a mistake to view this policy as punitive. You must know that it is never the mission of The Church, or our Heavenly Father, to harm or hold us back in anyway! The eternal efficacy of Temple ordinance is dependent on obedience to an eternal order established for the "benifit" of man-an order that we are trying to understand by attending the Temple. How can we dictate to The Lord how these ordinances should be conducted when we are at the begining stages of learning about the Temple?