[bobcowan]

That is correct. Although the spring lock washer does have it's place, it really only works once the bolt has come loose.

The purpose of a flat washer to to spread the load around the base material, and prevent galling. It gives the head of the fastener something to work against besides the base material.

Fasteners like the one in your picture are kind of a compromise. They have no real locking feature at all. They do spread the torque out on the base material. But they also work against the base material. They are cheap, and easy to use at the factory.