Ubuntu was winning on Desktop and they had to come up with something. And they did. They are following the EEE strategy, are actively trying to replace and undermine everything with tightly-coupled, in-house, break often technology. (In the meantime Canonical gave up, so there is no real need to destroy the desktop experience further further.)

(edit: of course Canonical was trying to control Debian in the meantime, so it's not like they are the Champion of Open Source here, just the underdog)