Split cakes?

I've been perusing the boards for quite some time now, and am seeing "split cakes" referred to quite a lot. I understand what they are, and how to make them, but am not so sure what they're for. (aside from rainbows) Can someone tell me what techniques having a split cake will help with?

Or is there a tutorial on how to use them somewhere?

https://www.youtube.com/watch?v=C2La5T9cN9U&feature=related

Watch this video. There are many on youtube with splitcakes.

Snakes, dragons, butterflies, flowers....

Split cakes basically just do your shading and blending for you, which takes a lot of the work out of the design. Consider Linda's pictures above. Those would obviously take a lot longer to paint if you had to add each color, blend, shade, etc... With split cakes, the work is done faster, so you can get more kids painted in your alloted time. This is especially good for ppf events when more kids = more money.

Check the face paint forum shop. Metina sells some, if you wanted a visual of what they look like