>>273806328
They didn't start with the same design. Oculus didn't have motion controllers at first, so their SDK likely was a little behind SteamVR on the input side. Then when they got motion controls, they actually had limited forms of finger tracking, which the Vive didn't really have. It was only until they came together to do OpenXR that they started developing a unified API that takes into account current needs and potential future needs of hardware and runtimes. 

>>273806489
What do you mean by that? I was trying to imply that they require a specific SDK to use and a specific API, that no other device uses, because the OpenVR API and Oculus API were developed separately for their individual needs at the time.