Usually, men’s shirts have buttons on the right, women’s on the left (there’s a few theories as to why). I grew up a tomboy, wearing as many hand-me-downs from Dad as from anyone else, so my closet’s always been a mix of men’s and women’s clothing, and I frequently forget which is which.
I’ve gotten it wrong before, but it’s the primary reason I usually “cheat” and draw only the seam with no buttons. 😀
Remember kids: No one cares why shirts are buttoned like they are.