I think the point of the 15 minutes is that if you accidentally bought it without realizing you were paying or if your kid took your phone and bought something there's a bit of a grace period before you're stuck with it. If you don't like the app, tough, if it doesn't work properly, wait for an upgrade and warn others.

This works more like a typo-protection (with the touch screens, I don't know what the equivalent of a typo is) not customer satisfaction protection. Given that most apps are under $5, a return policy at all is nice.