Why are there not more female conductors?

On September 29, the French conductor Nathalie Stutzmann made Irish history when she stepped onto the podium to conduct the RTÉ National Symphony Orchestra.
Stutzmann is remarkable not only for juggling a parallel career as a highly regarded singer but she is the first woman in the 91-year history to hold the post of principal guest conductor that will make her a regular visitor to the podium at the National Concert Hall during her tenure.