On a hammer fired gun, I can see the importance of having a firing pin block. In case the gun is dropped on the hammer (in either cocked or uncocked position), or the sear fails, the firing pin will be prevented from making contact with the primer due to the intervention of the firing pin block. However, on the Sigma, the striker is completely protected from impact, and is further protected from moving towards the primer by the presence of the sear itself.

So, help me understand why the striker block is an important safety device on the Sigma design.

Just a safety device to insure that the drop force of the pistol (like muzzle to concrete) doesn't allow the striker or firing pin to hit and set off a primer. The sear doesn't guarantee the striker from hitting a hot one when dropped.
Also, the firing pin doesn't need to strike a hammer to fire, simple inertia will pop a cap with a lite drop. Hence the safety plunger for the firing pin or striker.

It's to keep you from shooting yourself (or somebody else) in the ***, if the gun gets dropped. Irrespective of external hammers, inertia can move a striker or firing pin with sufficient force to fire a primer. Guns which have no hammers have necessarily heavier strikers, hence the advantage to adding the striker block.

I sadley knew a guy who got shot in the *** because his buddy dropped a snub nosed 357 in and out the left cheek very little bleeding

__________________
here comes the woo

I don't doubt that inertia can move an unimpeded striker with sufficient force to ignite a primer. However, I don't see the striker (in the Sigma) making it past the sear. The sear is thoroughly in the way of the striker moving forward.

I'll play....

1. May be a carryover from the G***k design on which the original Sigma was allegedly based.

2. May prevent the pistol from going full auto if the sear fails.

3. In the same vein, what does the articulated trigger safety add? Many documented accidental discharges on G***ks with a similar feature. Gun won't fire unless you deactivate the trigger safety by pulling the trigger?

But I haven't/won't disable either..... Is that where you're going with this?

The striker block prevents the gun going full-auto in case of sear/striker breakage, like Marlin said.

The articulated trigger on the Sigma prevents the pistol firing if dropped on its butt/rear of slide (you would have to drop it a long ways, I would think). In theory, on the Glock, the trigger safety would also prevent the pistol firing if only the edge of the trigger caught on a holster, etc.

Andy