Have you have ever tried to open a can of beans with an SAK? Tough job. Nothing in an SAK is designed to cut along the side of a can so you can remove the lid. A P-38 or P-51 does just that, with some effort. That's what is was meant to do.

Also, there are times when i jsut do not have any knife on me whatsover, because I cannot birng one with me, like on an air plane. No one looks twice at a P-38 or P-51. It would be of minimal use if you tried to use it as a weapon, unless maybe you had the person around the throat. Still, you'd need to hit the right spots.

In short, it is a useful little thing that you can bring anywhere, and if you have it on your key chain, like I do, it is with you all the time.