Most of the programs are not released yet. And there is no interactitivy, because Bonobo is not released yet, so they can't use embedded components like KDE does. They support StarOffice, because they can use their code. StarOffice's code can benefit both Gnome and KDE and speed up development. Gnome Office contains AbiWord, Gnumeric, Gimp, Achtung, maybe Evolution and Sodipodi, and probably some others as well.
Time is the issiue here.
KDE is older than Gnome. Gimp long before gnome and probably before KDE too. Oh yes, Gnumeric. Never intended to be part of Gnome. Oh and StarOffice, I wish they would stop stealing my applications and telling me they are gnome.