Exactly, the Linux crowd does things not for the common good or to gain market share, they primarly do things to scratch their own itch. If that itch happens to be plaguing others, then they get help. Gnome, KDE, they're both very good environnements with tons of features. They can replace OS X or Windows any day, but the people making these projects just don't care to go through the effort of marketing the product they made. They made it for themselves and they're quite happy using what they made.
I actually liked KDE 4.6 (tested it out on a VM in my Mac, Virtual Box did an amazing job giving the VM access to the 320M for hardware accelerated compositing) after 4.0 had completely turned me off.