I kind of like to think of Santa as a "god training wheels" for kids. First, the concept introduces them to the idea of modifying their behavior for a delayed

I kind of like to think of Santa as a "god training wheels" for kids. First, the concept introduces them to the idea of modifying their behavior for a delayed reward. Secondly, they can practice in a belief system with the freedom of making mistakes, without offending / blasphemy against a real deity (because that would be bad). Once they get beyond this simplified system, they can move on to interacting with a real deity.