The Last Confederate hit the nail on the head:
The only thing that limits the uses for the blades in an SAK is the imagination of the user.
The greatest thing about SAKs and multi-tools is their ability to create other survival equipment from scrap.
Unfortunately, trash is all to common in the lower 48 states...seldom do I find some wilderness without the telltale signs of previous visitors (trash, lost gear, broken camping items, etc...).
With a SAK or a multi-tool, and a little imagination, you can use this stuff to help yourself out in any situation.
A piece of barbed-wire or a nail can become a fishing hook...
An aluminum beer can might be turned in to some fishing lures, or a "hobo stove"...
Plastic, fiberglass, or metal pieces of junk can be fashioned in to arrowheads...
And the pliars are useful for cracking nuts and shells...
The list is never-ending.
A SAK or multi-tool is the thinking man's survival knife.