As far as I know, only SuSe promotes KDE, and majority of other distros promote GNOME.
I would like to mention Ubuntu - this distro strongly promotes GNOME, although Mark Shuttleworth said he preferes KDE. Tell me, why is this the case?
In my opinion, it's easier for developers to create KDE (or Qt-base) applications, because Qt framework is object-oriented and similar to .net or java. This makes a lot easier to new developers to create applications in Qt.
On the other hand, creating gtk applications is real pain in the ass. First of all, gtk is only pseudo-object-oriented, and awkward long function names (think gtk_tree_path_new_from_string) repel all new developers away, especially if they are used to easy-to-use frameworks for GUI creation, such as .NET or Java Swing.
Personally, I think that promoting GNOME is Microsoft's secret agenda of promoting Windows as really easy to use your computer. Notice the similarities between Windows7 and KDE4. They look almost the same. Why? Because Microsoft found out that KDE4 has some very nice features that would be nice to have in Windows. What did Windows "import" from GNOME? Nothing.
So, the plan is simple:
- use your pal Novell to finance the KDE project and use their ideas for windows, but make sure KDE is never stable enough for average end users
- make sure Red Hat, Canonical and other Linux vendors promote GNOME, so all new users will give up linux when they found out that they can't add new keyboard shortcuts, change desktop effects or configure sound server without installing additional software