Aren't door knobs supposed to be on the right hand side of entry doors?

Most people are right handed. Which makes it easier to open the door if the knob is on left side, because after the door is open then your right hand is on the same side of your path as the door :). If the area left and right of the door is kind of narrow, it is also easier to use a key if the lock is on the left side of the door. If on the right side, your arm would easily bang into the "whatever" is next to the door. When lock is on left side, you get the entire door width as your "working space".