Perhaps this rule will help you understand why an asymmetrical shaft is against the rules of golf - from the USGA website:
"Appendix II, 2b requires that: At any point along its length, the shaft shall: bend in such a way that the deflection is the same regardless of how the shaft is rotated about its longitudinal axis; and twist the same amount in both directions. This rule effectively restricts shafts from being designed to have asymmetric properties, so that however the club is assembled, or whichever way the shaft is orientated, it will make no difference to the performance of the club. However, most graphite shafts have a small "spine" running along the length of the shaft which does make them bend a little differently depending on how they are fitted to the head. This is generally regarded as being "within manufacturing tolerances" (see preamble to Appendix II) and therefore not a breach of Appendix II, 2b. Manufacturers of clubs may orientate or align shafts which have spines for uniformity in assembling sets or in an effort to make the shafts perform as if they were perfectly symmetrical. However, a shaft which has been orientated for the purpose of influencing the performance of a club, e.g., to correct wayward shots, would be contrary to the intent of this rule."
