Effective April 1, 2018, all app updates for Apple Watch must be available for watchOS 2 and newer, and new apps must be supported by watchOS 4 and newer.
Apple will stop releasing app updates for watchOS 1. Additionally, the watchOS app size limit has been increased from 50 megabytes to 75 megabytes.
The company wants to clean App Store of applications that are not intended for the latest versions of the system. This is the right decision as the original Apple Watch and watchOS 1 SDKs were test products.
Apps for WatchOS 1 are slow, awkward and downright ridiculous. Apple tried to fix all the issues regarding the watchOS SDK version more than once. WatchOS 2, for example, introduces early releases of final features.
With the release of watchOS 4, developers can create apps that run independently of the associated iPhone and use an internet connection.
watchOS 4 is also faster with new navigation and audio recording modes, built-in altimeter, direct accessory connectivity, and more.