Ubuntu is the name chosen for a global project and a distro based on Gnome. Kubuntu is another distro based on kde from the very same project.
I believe they deserve the same support from the project since Gnome and Kde are the most popular desktop manager out there.
It seems quite obvious to me, the project is very much focused on one and only distro, its first baby : ubuntu.
And it shows. Kubuntu web site looks quite poor and unprofessional compared to ubuntu. Most graphic choices like the kdm default theme (even if it's supposed to be a matter of taste) look, again, unprofessional. And finally the whole distro doesn't seem to have the same amount of attention when it comes to details (one example among others: the little thing on ubuntu warning the user about the existence of proprietary drivers for display which does not exist on kubuntu).
I've been told once, like a year ago, by an ubuntu dev that the situation is such because the project doesn't feel like fragmenting its market share.
Whatever is the official position of the project, I don't think you should do things half way.
The Kde project is itself in full evolution with Kde 4. It does deserve full support from ubuntu.
Thank you for reading.