They did so, because 3D Touch allows for users to press firmly on a notification, which have been optimized for the pressure-sensitive displays needed to use 3D Touch, to bring up more content from a notification without having to unlock a device, or dig into an app. Fortunately for those who have not upgraded to one of Apple’s newest flagships, and for those who don’t plan to upgrade in the near future, rich notifications work without 3D Touch-enabled devices, too.
The company confirmed the support for non-3D Touch devices in beta release notes for Rich Notifications, as reported by MacRumors. However, Apple does say that rich notifications are optimized for 3D Touch, and, as of right now, the feature is only available for the iPhone 6s and iPhone 6s Plus in the early beta stages. Support for non-3D Touch devices will arrive later, and in time for the public launch later this year.
“Support for rich notifications is optimized for 3D Touch, and in iOS 10 beta 1 the feature is available only on iPhone 6s and iPhone 6s Plus. Future betas will provide access to this functionality for users of iPhone models without support for 3D Touch.”
Unfortunately the release notes don’t articulate how the feature will work without 3D Touch, but it would seem likely that a long-press of some length will probably be the best way to make it a reality.