From Elven Blades and Zero-G Ki: The Evolution of Martial Arts in SF and Fantasy:
Lord of the Rings comes from an early period in the development of the fantasy genre. At that time, the convention was that the only thing necessary to make an ordinary person into a warrior is a weapon. Similarly, in C. S. Lewis' The Chronicles of Narnia, the gift of non-magical swords and bows endows English schoolchildren not only with battlefield competence, but with mastery.Very interesting article. Found out about it in a USENET post I found on Google Groups.
Genre conventions have changed, and now the "training sequence" is almost obligatory in novels in which previously untrained characters end up fighting. Mirroring the evolution of the wizard from ancient Merlins and Gandalfs of mysterious origin to Ursula K. Le Guin and J. K. Rowling's youngsters in wizardry schools, writers began paying attention to how warriors, those other standbys of fantasy, learned to do what they do.