Oh, serving you more relevant ads based on who you are so you purchase products isn't about you? :P
Okay, here's a stupid realistic answer: It might help stop kids from making purchases on adults phones without the actual adult.
But that's not a good answer even if it may be a side effect, because they aren't doing it to help us, they're doing it to own us. We rent our time here and have to work for it. They were born to never have to do anything but take our money, time, lifeblood, sanity, leisure, resources and potential. Simple really.