Answer: In those days, only rich women wore shirts with buttons, and they didn't do it themselves; their maids would do it for them. And since most people used their right hands, the buttons had to be on the left side to make it easier for the person standing opposite to button them up.

In the past, when men were in charge of hunting, the movement of bringing the weapon when shooting was usually from left to right, so the buttons and fasteners on the clothes were designed on the right side to match the direction of the body's movement.