Why does Ubuntu still require restart after kernel updates when tools out there mean it's unnecessary? [duplicate]

A regular occurrence in updating Ubuntu is kernel updates, which require a restart. There are applications which negate the need for a restart after a kernel update e.g. ksplice.

Why doesn't Ubuntu use tools similar to ksplice? Are there security, memory, etc. concerns to not restarting immediately/ever? Or, can these issues be overcome (i.e. are they just bugs)?

I found this IRC log from Feb. containing a question and answer session with Peter Graner (pgraner), the Kernel Engineering Manager:

<Taek> QUESTION: Is there plans or even talk about having a system update without having to restart or install third party software such as ksplice.

<pgraner> Taek, the kernel will support kplice however we have no plans to do such a thing, there is already a commercial venture that does that

<sebsebseb> QUESTION: Do you think that Ubuntu Desktop might use Ksplice in the future?

<pgraner> sebsebseb, No as stated in the last question

Not really a satisfying answer to the why, but the best I could find.

It may be patent encumbered:

http://www.google.com/patents?id=cVyWAAAAEBAJ&dq=hotpatching