There was a time when I thought of moulding and trim as purely decorative. If you've ever replaced a floor or door, though, you realize their purpose is more to hide inaccuracies in cuts and joints. There is the issue of allowing for movement and expansion, but the sizes of the gaps commonly found is more than enough. It would probably look strange to us, but imagine a house with supreme fit and finish, with only 3/4" strips of trip around edges.