Debian has a working Edu environment with LTSP, meta-packages with pre-selected software and everything - why should anything like that be ported from Ubuntu?
Maybe because Edubuntu meta-packaging is better than that of DebianEdu.
However this is just my opinion. Everybody is free to have his opinion.
I'd prefer to use Edubuntu rather than DebianEdu, and of course you don't
even want to hear anything about Ubuntu.
Dashamir