What it actually shows is totally inaccurate, becuae the wheels move in and out as they move up and down, and your drawing doesn't show that at all. It is totally misleading, and makes it seem like the spacers do something useful, when if fact, the don't.

 

No they are not! Take the springs off your car, move the suspension around, and measure at different positions, and you'll see for yourself.
(Or you could just read the thread that was linked to earlier.)