If you ever wondered what a rejection letter from Apple looks like. Here is one I got.
We found that the features and/or content of your app were not useful or entertaining enough, or your app did not appeal to a broad enough audience, to be in compliance with the App Store Review Guidelines.
For example, your app includes a very limited set of features. Specifically, your app simply allows the user to take images in black and white.
We understand that there are no hard and fast rules to define this but it can be helpful to look at the apps featured on the App Store to get a feel for the type of experience our users expect.
It’s true that my app didn’t do more than make black & white photos, but it was very simple and most importantly completely free and without ads.