This is a valid question, I am a developer and have been struggling with this issue.
See, iOS7 makes it harder to be backward compatible than previous versions of iOS. iOS6 compatibility is not as big of an issue as iOS6 already had introduced layout APIs (autolayout) that simplifies layout management for different systems (screen sizes, layout changes between different versions of iOS,etc...).
But making apps compatible for both iOS5 and iOS7 can be a real challenge, so many developers talk about dropping support for iOS5, which would drop support for iPad1. We are not excited about that as we have many customers with iPad1, but we have only so much time to make everything work...