mostly as squares and rectangles and variations on squares and rectangles? Just once in a while people have built houses in other shapes - such as the occasional round house "to keep the devil out".
I suspect the simple answer to that question is "it's easier and cheaper and our things fit more easily into those spaces". Our house is exactly like that. It is, in a sense a squat rectangle with a longer rectangle on one side or the squat rectangle.
As houses go it is not inconvenient and it is only about thirty years old. My parents built it for their retirement.
It has certain features which were designed for their old age. Like most Australian houses it is all on one level. You do not climb the stairs to go to bed. The house is, as we have proved, accessible for someone in a wheelchair. (I cannot say the same of the back garden but you can get to the Senior Cat's workshop.)
The house itself also has another important feature. The city I live in is built on a major fault line. There was a quite serious earthquake in the region when I was a small child. I can remember it in that I can remember lying in bed and watching the wardrobe swaying backwards and forwards before my father came and carried me out into the night. I can also remember putting my small hand into the crack in the wall of the house belonging to my godmother's mother. Since then houses are supposed to have more protection against earthquakes. Of course not all of them do but ours was built with a particular type of foundations and the house itself rests on those in a way that is supposed to minimise earthquake damage. How much protection it would actually afford is something I hope we never have to find out.
But, that is earthquakes. There is no such protection against something like a tornado. We do have tornadoes in Australia but, at least so far, we have not had the sort of appalling damage that they have just had in Oklahoma.
It is that damage which makes me wonder about the way in which houses are built. The Whirlwind had a school project a little while back in which everyone had to design a house. They were told that money was no object but the house had to be environmentally friendly. There were some extraordinary ideas, interesting ideas, unworkable ideas, sound ideas and strange ideas. The Whirlwind's house was round, looking in on a central courtyard. She knew it would be expensive to build but, apart from that, it was a house that could well have been lived in. A friend of hers designed something that was similar but octagonal rather than circular. Again it would have been expensive to build but it could well have been lived in.
Looking back on those houses I wondered whether they would be more earthquake proof or tornado proof or something else proof. There is a house not too far from here which is a dome shape. It was an architectural experiment. I have no idea what it is like inside or what it would be like to live in but the architect designed it with the fault line in mind.
And, looking at the horrendous damage in Oklahoma, I am wondering whether we should perhaps start to think about other shapes for building houses. Would round houses help to keep the devil-wind out? I don't know enough about physics but it is something I like to think about.