Very true. Nokia seem very reticent to provide this port themselves, and are waiting for someone else to do it (Sun or another third-party).
It may only be a matter of time however, as the user base and notoriety of Nokia's tablets expand dramatically with each iteration. In 2005/2006 the 770 was very confidential and mainly a geek toy. This year the N800 was more heavily marketed as part of the N series, more widespread and easily available. Now it seems the N810 is going to be all over the place :-)
Also, the Nokia/Maemo team's relationship with upstream projects (GTK, Gnome, embedded-gnome & mobile-Ubuntu etc.), its developer community and user base, has had its ups and downs but seems to have found its way, and is paying off handsomely in the latest (4.0) version of the Tablet OS...