With adding the large number of bug fixes / new unique features apple moved to iOS 9 beta 1 version on last WWDC meeting. Along with IOS 9 release, Apple released Watch OS 2 and OS X Ei Capitan. iOS 9 had especially placed because it is world-leading mobile operation system and millions of users are taking advantage with it.
After release iOS 9 beta 1, millions of users install it via Developer account and UDID account. However, shortly those users are finding method to downgrade to previous and especially for iOS 8.3 version.