Ubuntu works very hard to only distribute one app for one job. Yes, the Open Source world provides loads of choice - which is why we have repos... but for the simplicity and tidyness of Ubuntu, this rule is essential.
No matter what distro I've been using, I have always hated KDE, even though it has many strengths over Gnome, and I've always hated it for one reason - there are *far* too many icons on a default install. I would love to fall in love with KDE, but that's just not going to happen until I can install a KDE desktop with a sensible number of icons, and without 4 different programs to do everything.
So, my idea is, that Kubuntu also adopts the one app for one job policy, and seriously cuts down on the number of apps it provides by default. I can install more if I need them.