During the Renaissance and Victorian periods, women’s clothing was more complex compared to men’s. Due to this complexity, women were often dressed by servants. The buttons on women’s clothing were placed on the left side to make it easier for the servants to button them up. Men, on the other hand, usually dressed themselves, so their buttons were on the right side. This practical arrangement eventually became a standard.
Although it is quite rare today for women to be dressed by servants, this tradition continues. The main reasons for its perpetuation are that most people do not notice this and do not complain about it.
Alternative theories explain the reason for the button placement
According to alternative theories, buttons may have been placed on the left side to allow women to easily button them with their right hand while holding a baby with their left. Additionally, buttons may have been designed this way to provide wind protection while riding horses.
In men’s clothing, buttons are generally on the right side because they usually carried a sword on the left; this arrangement facilitates easier movement when drawing the sword.
Source: The Atlantic, Smithsonian Magazine