I have been shooting with both eyes open for as long as I can remember. In my adolescents, I was enrolled in cadets where they had a shooting range. My first time there, the range officer noticed I was shooting with both eyes open and proceeded to yelling that I was doing it wrong and should have one eye closed.
After "hearing him out" I tried with one eye closed and couldn't hit the side of a barn for the life of me... more screaming and yelling followed. This guy was a knob... a complete ***!
Once he was done, I went back to both eyes open only to hear him praise me for the terrific shooting. Proudly, I yelled, "That was with both eyes open! Wanna see me try again with one eye???" Needless to say, he shut up rather quickly and to this day, I still shoot with both eyes open. It's just habit... not comfort or any other reason.