You can use your front sight while not having to focus on it. Pick an object in the room then point your finger at it while staying focused on the object. You can plainly see that your finger is there in the unfocused foreground pointing directly at the object even though you are not focused on your finger. You can do the same using just your front sight in close encounters.
My carry piece has high visibility day or night front sights. Should I be attacked by some assailant and require drawing my weapon, I want to know exactly what that assailant is doing – what are they doing with their hands, do they have a weapon visible, are they coming at me. I can’t tell if I’m busy trying to focus on my sights.