here's the interesting thing (that is to say interesting if you draw rooms and doors for a living, which is probably not that interesting at all). Sliding doors don't save space. They sterilise a length of wall to one side of the door opening.
I beg to differ.
One could argue that this perception comes from a rather eurocentric view of what 'walls' and 'doors' are for and how they are, or should be, constructed. For example, Japanese internal wall construction means that walls and sliding doors (there's actually not so much distinction between the two anyway, so it would probably be better to refer to them as door panels and wall panels) are often translucent but not transparent. Sliding a panel across another changes the quality of light somewhat - and that's part of the point. It doesn't 'sterilise' anything, quite the contrary. Most Japanese furniture is lightweight and moveable and painted art, if you have such a thing tends to be on screens or scrolls which either have a very particular place (not affected by a sliding door) or no particular place at all (i.e. they can be anywhere). Where there are opaque panels, posters and suchlike flat things, if you do have them on a wall panel, aren't bothered by the sliding doors,as they sit in a track which tends to have a good cm of space beween sliding panel and wall panel.
And, BTW, if you think three rather than two-dimensionally, conventional western doors create a quarter to one half cylinder of dead space from floor almost to ceiling, and also affect the use of the wall behind (if that's a problem for you).