Lack of interest from Canonical. There is nothing preventing them really from
doing better on the KDE front. They have money to work on it. The Qt licenses
changed in the past year to be both GPL and LGPL for the KDE base. Lots of
interaction is happening between Nokia (owners of Qt now ) and KDE developers
to push it forward onto smaller devices.
The only answer is to switch to a better supporting distro. Other distros with
less money behind them seem to being doing a much better job with KDE, as well
as supporting/providing other window managers.
Ubuntu is okay, but I am not impressed with this lack of support for anything
but GNOME. Ubuntu is overrated in my opinion. Kubuntu is(was?) okay, but
I really cannot agree that it was all that great compared to the KDE offerings
of other distros (it's artwork/themes actually looked rather slack to me).
Mandriva, SUSE, and others are definitely better.
There is a lot of hype surrounding Ubuntu and its ilk. And lots of people are
falling for this without any substantial benefits to justify it.
Raymond