They are common up here in northern Ontario in Canada ... but it's just a habit with people up here ... everyone prefers using the back door and when you get there, you knock on the door. The front door is more or less decorative and seldom used and usually used only for days like Halloween or mail package deliveries (and package carriers are better as they almost always use door bell)

People are in fact just that fucking retarded. They just don't think and react extremely slowly to even the most common of stimulus and information of their surroundings.