It drops the hammer safely on a double action semi auto pistol to make
it more like a revolver on the first shot..
Most Glocks and guns that are inspired by them, don't leave the hammer
cocked after each shot and it is always double action.
The thought originally was it was an easier transition for cops that
had a six shooter all their life.
I guess you could call the striker "the hammer," in that they serve a
similar purpose. Still don't much like carry pistols or even defensive
pistols sans safeties or decockers. Even my Ruger 22, which fires rounds
via what might be called a massive moving striker, has a safety.