if it takes care of itself, whats the big deal?

The side effects:

As for the W32/Lovsan.worm, some systems may be in a “crash loop” where each time the system is restarted, SVCHOST.EXE crashes and the user has 60 seconds before the system restarts. This action can continue to happen even after the virus is removed if the patch is not applied.

Basically, the exploit might fail, leaving the patch unapplied and the system screwed.

Gareth