It’s as if a handwritten signature, even in PNG form, has a magical superpower to make a document authentic. A bit like the security theater at entrances to buildings and transport.
While Germany cards doesn’t seem to have a digital / smartcard component, French ones do. In Portugal and Spain at least you’re required to sign digital documents with your identity card, using a smartcard reader + a small utility app provided by the gov. Only those have legal value and this is enforced. Scanned handwritten signatures have zero value, and I know this also applied for other EU countries.