Dividing Pizza dough to balls before baking
Probably so that the gluten can relax before you go for the final forming. 

By forming it into a ball you are starting it towards "pizza pie disk shape" from "formless mass of dough." If it rests for 10 minutes or more in that shape, proceeding to further shape it into a disk will go easier (and further, if desired), with less spring-back from the gluten network.

I use roughly the same process in making bagels or long strips for braiding. You can work it until it just won't go anymore, take a break, and come back to find it pliable and willing to stretch further.