Advantages of Interoperability?

When we can get good speed with OpenGL since it uses texture memory and many inbuilt graphics functions(blending,mip map etc).

Why do we need OpenCL(slow beacuse of openCL buffers) interoperability with OpenGL just because the we can combine rendering with computation or are there any good advantages like performance.

I just wanted to know the main advantage of this and are there any published papers that shows that they got increase in performance by using OpenGL interoperability with OpenCL or any proof that showed increased in performance in terms of speed and quality.

Best Regards