Rob Tisinai explains a category error:
No thing has a purpose; people have a purpose for things. It’s an easy and honest trap door if you find yourself in a rhetorical corner. … The moment I hear “The purpose of…” I know somebody’s trying to get something past me. If purpose doesn’t reside in a thing, but in the intent of the person, then a thing can “have” as many purposes as there are people. What’s the purpose of sex? Procreation, intimacy, recreation, revenge, validation, profit. And many, many others.
The Dish 