Why do microwave trays turn? This is a stupid question, but I other wondered why. Why?

This is a stupid question, but I other wondered why. Why?
Sprouting seed and Vegetables?
Answers:    To evenly distribute the heat top, and make for more thorough cooking. I presume they cook from the middle out, so when the tray turns, no one place get zapped more than the other so you don't have to continually rotate or turn what you are cooking.
My cactus broke how do I keep hold...
to cook the foods evenly.. it have to do with roast wave. It is also mush easier than have to stop the microwave and rotate your food...So to have the trays turn itself is pretty awesome and handy too