Why do most Japanese houses have sliding doors?

I just want to know why sliding doors were used and what was the material that they used on it? Was it tissue paper or thin fabric? What was the significance?Why do most Japanese houses have sliding doors?
Space and material...the style goes back centuries and it was easier to build a sliding door than to deal with hinges.





The material is a type of rice paper which is cooler in the summer...part of the cultural heritage is self discipline and keep your self control meant not raising your voice which with paper thin walls, everyone would know that you lost control....





Mainly it had to do with material availability....Why do most Japanese houses have sliding doors?
Mainly because of the space needed to open a door. The wasted 9 square feet could be put to better use. Also the use of Shoji doors allow multiple rooms to be opened up into a larger room. Shoji screens are free standing screens within the room.





The white stuff is rice paper.
sliding doors are called pocket doors, and they come in handy and don't take up as much room as a door that needs to 'swing open'; for access.