The German ID also has an online verification function already in it, but if you are a Spanish citizen for example on holiday in Germany that doesn't help you.

The German ID also has an online verification function already in it, but if you are a Spanish citizen for example on holiday in Germany that doesn't help you. One EU-wide system is much better than a different one for each country as it helps to give equal access to online services regardless of your country of origin. That system is mostly just used for government websites, stuff like getting a new passport, change your registered address or view/submit your taxes. If you could do this stuff anywhere in the EU online no matter where you are from it would be way easier to move between countries and navigate different bureaucracies.