This is just because EVERY SINGLE GUARD in the game wants to go have whiskey and cigars. (bitcultures.com)
The design features a central viewing chamber with a system of mirrors that allows a single guard to keep watch on the entire prison population in their cells. (blog.politics.ox.ac.uk)
You've got a number of weapons to lethally take down aggressive guards, but they all feel puny and ineffectual, taking four or five shots to down a single guard on the Normal difficulty setting. (polygon.com)