Weird. I was surprised to see in a couple of houses that you had to go through the kitchen to get to the bathroom. I thought that was really strange!
This is typical of older houses. In many cases what is now the bathroom was a coal shed or kitchen pantry. This is b/c the houses would have originally had outdoor loos!! Houses like this don't have to conform to the newer fire codes.
I think Pebbles is right, the doors are primarily fire code stuff though there's probably something to the divison between kitchen/bathroom thing, too. The doors also have to do with heating. Before central heating, you would always have your doors shut to keep the heat in the room where you were. Unfortunately it's carried on into new builds because that's what people are used to. Drives me insane. We were in a tiny flat in Exmouth at one point. You could heat it in the dead of winter just by making toast. But every room had a door! DH and I took most of them off the hinges and stored them in the garage until we moved out!
And the doors opening in was insane in that flat, too. The kitchen wasn't big enough to swing a cat in but the door opened in to it!!
