A universal API would make life a lot more easy for developers.
A big problem in the modern technology space is computing, gaming and programming for separate devices whilst trying to maintain some form of working cohesion. Currently, and more often than not, devices all carried their own unique API that lets it do whatever it was designed to do, but this led to problems when it came to cross device interaction.
Microsoft are aiming to change this with a Universal Windows Platform that will ensure all API are universal, allowing for cross device and platform functionality. Whereas the Xbox One, Windows Phone and Windows OS all have their own API, the goal is to boil this down into one, jack of all trades API. Basically, if it works on one device, it will work on them all.
Microsoft Universal Windows Platform Program Managers Brent Rector and Peter Torr have said that it should be, “One core platform” that supports all devices if they can fully realize something that can be considered, “truly a single code base”.
Source: Build 2015.