Abruptly popping out around the corner exposes our entire body and takes us extra time to get the weapon on target.
When clearing a corner, our goal is to be able to clear the area around the corner while exposing as little of our body as possible.
One of the ways this can best be accomplished is by pushing back off the wall and then methodically working our way around the corner leading with our head and the weapon.
If a threat is spotted, we only expose what is necessary to engage the target, keeping the rest of body behind cover.
The farther back off the corner you are, the better angle you will have on the target, possibly allowing you to see them before they see you.