Google introduces Android Go

During I/O, Google also announced Android Go, a version of the mobile operating system optimised for lower-end devices. From Google's announcement:OS: We're optimizing Android O to run smoothly and efficiently on entry-level devices.Apps: We're also designing Google apps to use less memory, storage space, and mobile data, including apps such as YouTube Go, Chrome, and Gboard.Play: On entry-level devices, Play store will promote a better user experience by highlighting apps that are specifically designed for these devices -- such as apps that use less memory, storage space, and mobile data -- while still giving users access to the entire app catalog.If a device has less than 1 GB of RAM, it will automatically use the Android Go version of Android. In addition, Google has set up a set of guidelines applications must adhere to in order to qualify for the special highlighting mentioned above.The first question that popped into my mind was - why isn't every device getting this supposedly faster, and more lightweight version of Android? Will we be able to 'force' our devices to use Android Go, even if they don't officially qualify? The second question is - why would a developer go the lengths of creating additional versions of their application, instead of what they ought to do, which is slim down their existing application?