I've always had layers on the bottom, whether my hair is short or long. It just looks better in wavy and curly hair in my opinion. You don't need layers all over the place, just on the bottom will make your hair look less thick, if that's all you want.

Thinning isn't the same as layers though. You don't have control of where your ends are with thinning, because it's so random. And I heard it can cause split ends with all the rubbing, most people I talked to didn't like it.