I'm partially upstream and partially Debian maintainer for a certain package.
The Ubuntu maintainers for that package and similar packages are the "Masters of the Universe". Those great masters never seem to triage bugs and forward bugs upstream. Debian packages should (and mostly do) follow up on issues and update upstream. The Ubuntu Universe packages tend to have no real maintainer.
And it is not the job of upstream to triage Ubuntu bugs. Upstream is not qualified to guess that Ubuntu Beastie Barbie is actually ubuntu 5.999 and this naturally implies libc6 2.11, libken 1:5.21 and liberty 3.14159 . Yes, those would be trivial to find from http://packages.ubuntu.com, but does upstream know about that? Does upstream know that it is actually a good idea to ask about sources.list because the user might have tried to upgrade?
Upstream should not need to face the specific quirks of each distribution. This is what packagers / power users are for.