WHY did women start wearing high heels?

 As it turns out, the first to wear high heels were not women, but men. 

Due to their ability to secure the rider in the stirrups, they were the most comfortable shoes for riders. The first lady to wear heels was Catherine de Medici, the Duke of Orleans's spouse.

She wanted to highlight her high status, so she specifically requested that high heels be produced for her.