I think Mercurial also misses the mark for uploading patch sets which might evolve / change over a few iterations. The workflow usually looks like one user is working on only one set of changes at a time, and in order to show them to upstream they want to publish them somewhere. If these changes get edited several time, and you use a traditional Mercurial repository you end up with lots of zombie tips which you absolutely don't care about, and unless you 'hg strip' very assiduously, they keep reinfecting repositories.
Yes, I know it's not a supported workflow. No, sometimes, this is what I want to do.