In Integrating with Existing Apps guide and

Note that running on device requires Apple Developer account and provisioning your iPhone

Not every app uses all the native capabilities, and including the code to support all those features would impact the binary size... But we still want to make it easy to add

There are tons of native UI widgets out there ready to be used in the latest apps - some of them are part of the platform, others are available as third-party libraries, and

Sometimes an app needs access to platform API, and React Native doesn't have a corresponding module yet. Maybe you want to reuse some existing Objective-C, Swift or C++ code

Since React makes no assumptions about the rest of your technology stack – it’s commonly noted as simply the V in MVC – it’s easily embeddable within