I accept and agree with the statement "detailed commit messages and pull requests with context are objectively more useful", but I don't see how GitHub fails in

I accept and agree with the statement "detailed commit messages and pull requests with context are objectively more useful", but I don't see how GitHub fails in that regard any more than Git does. You can have horrible commit messages and pull requests using e-mail pull requests. You can have the same with GitHub. Ultimately, the decisions of what sort of quality you demand on pull requests ought to be up to the maintainer, and GitHub is doing the right thing by not enforcing a standard that doesn't work for the majority of people.