This is an example in which history seems to matter. When buttons first appeared in the 17th century, they were seen only on garments of the wealthy. At that time it was the custom for rich men to dress themselves and for women to be dressed by servants.

Having women's shirts button from the left thus made things easier for the mostly right-handed servants who dressed them. Having men's shirts button from the right made sense not only because most men dressed themselves, but also because a sword drawn from the left hip with the right hand would be less likely to become caught in the shirt. Today, virtually no women are dressed by servants, so why is buttoning from the left still the norm for women?