What is the purpose?

So Tayla has a really cute outfit on today that she has never worn before. As I was getting her dressed I noticed some stitching on the leg of her pants. I checked and sure enough it is a real pocket. But some one please enlighten me, what is the purpose of said pocket? Nate has a similar pocket on his pants; it's a cell phone pocket. But once again what is the purpose on pants that belong to (mine and others similar) babies that can't talk.