This has been a real head-scratcher for me over the past week as apps have been updating in advance of tomorrow's iOS 7 launch—why would TextExpander need permission to access my Reminders? Smile's blog explains that there's a very good reason:
When you update to iOS 7, you may find that TextExpander doesn't work in some apps which did work on iOS 6. Due to a change in iOS 7, those apps no longer have access to shared snippets. We have communicated with developers whose apps support TextExpander, and we've provided them an updated SDK with a new way to share snippet data.
In short, Apple has decided to break the way your snippets used to be shared between apps. Smile's solution is to store the data in your Reminders—because they're accessible even in the highly sandboxed environment of iOS. In a way, it's sad that developers have to figure out inelegant hacks like this one in order to provide basic functionality, but at the same time it does demonstrate the ingenuity of the developer community.
I wonder how many users will be refusing to give the app Reminders permissions and then writing support emails to Smile, complaining that the app doesn't work. What an (unavoidable) support nightmare.