For example, I'd like to see Python's async frameworks building on ASGI middleware rather than all re-writing their own middleware APIs. That way we end up with lots of cross-framework compatible middleware implementations, and we're all working together much more coherently.
Similarly for test clients. We don't really need frameworks to all be building their own individual test clients to interact against their own interfaces, when we can instead build test clients to interface against ASGI, and then be able to use them against any ASGI framework.
That's part of what the Starlette project (which Responder uses) is all about: https://www.starlette.io/
(FWIW Starlette also composes all those bits and pieces into a framework in its own right)
From what I understand ASGI was developed by Andrew Godwin for Django Channels.
But just thinking about my own experiences, being able to look at what other people have done so far with it would help immensely when building the nuts and the bolts of the feature. This project will help immensely with that.
This is how we get to async Django, and I think that's part of why Tom Christie is helping out. I also doubt Reitz thinks this is the usurper of Django anyway. It's more than an experiment, but less than "the new One True Way".
As for ASGI python web frameworks, there are no mature winners in the space yet (compare uvicorn's quickstart example to this project's before you throw that project out as an example). This is Truly New Shit, and I'm pumped these two devs are working on it together.