On Sat, 22 Apr 2017 08:25:36 -0400, wrote:
So convention has been to use vertical button holes
except where the button hole is likely to be out of
sight. This is typically the bottom most button hole
(tucked into your pants) and sometimes the topmost
button hole also (under your tie, or unbuttoned)

Another reason for vertical button holes is the designed width of the
faced material section down the front of the shirt, and the button
size choice. Vertical button holes may just be practical.

--
Maggie