Implementing a functionality for e.g. the danish national ID with a few million users, or Luxembourg, or Austria, isn't worth it. So you'd have support for Fra

Implementing a functionality for e.g. the danish national ID with a few million users, or Luxembourg, or Austria, isn't worth it. So you'd have support for France, Germany, maybe Netherlands, and that's it. With an EU-wide ID, the smaller countries profit significantly, and startups can integrate and use the functionality easier.