I'd don't really see a difference between sending an email to a list or to a maintainer. Maybe that's an argument for not adding and adapting to unnecessary concepts like a web based pull request.
> How do you build any sort of community without a place for discussion?
There exist many ways for this. Why does this have to be the same provider (if you don't want to self-host this functionality) as the one that hosts the server for the VCS?