Owning an iPhone isn't just a software choice: It's a hardware choice as well. A large part of choosing hardware is the aesthetic value that comes with it, which puts a lot of people off of stuffing their phone into a thick, bulky case in order to protect it.
The Peel case is designed to appeal to those who want protection without sacrificing the look of their iPhone. It's ultra thin, so it won't protect against serious abuse, but it's better than nothing. Peel says its case will guard against "light drops, dirt, and scratches," which is honestly all most of us need protection against.