The exact use for this, as far as I know, so correct me if i'm wrong. But it can be used for a couple things.
1) Smashing windows to gain entrance to a car for example
2) To prevent the slide/barrel from being pushed back by a persons hand or driving it into their face which can prevent the gun from properly firing.
I suppose other uses can come of this as well, others have said it to be an 'anti suicide' device because it might cause undesireable pain with the sharp points when driven into the side of your skull as you deceide to pull the trigger. But the most important thing, it looks bad ass lol.