I was there when the OpenCL committee was deciding on that sort of stuff.
As I recall, and it's been two decades and a lot of sleepless nights since then, there was real pushback at the time against OpenGL-style default bindings. So folks didn't want to establish an implicit command queue or any other default objects attached to other objects. Part of it is because OpenGL was perceived as clumsy and passé, some of it was because it is not friendly to multi-threaded applications.
Those first meetings were a shitshow full of tension, implicit threats from Apple, and backroom deals. Kudos to Neil Trevett for chairing the group; I I bet it wasn't fun for him either.