Men’s buttons are on the right to make it easy to do up with one hand for right-handed people.
When buttons were invented, only the wealthy wore them. Wealthy women had maids who would do the buttons up for them, and so the buttons are on the left so that they are easier for someone facing you to do up.
That’s interesting. I never would have thought of this. I use two hands to button and never considered what side anything was on. Perhaps because I have both men’s and women’s shirts?