There are two PINs, PIN1 for ZKP and PIN2 digital signing. The card does nothing without one.

Most EU countries provide some way for citizens to sign documents using a private key tied to their legal personage.

Putting it on the ID card they are given anyway just makes sense.

My final paragraph is there to explain that a lot of “digital signatures” aren’t really signatures in any meaningful way. What goes into the actual file doesn’t matter at all, UNLESS it’s the aforementioned cryptographic signature.