My country already has an advanced e-identity system. Why should I instead use the EU Digital Identity Wallet?

The EU Digital Identity Wallet will supplement and not replace existing eID schemes .
Your country might promote use of the EU Digital Identity Wallet over eID because it has additional features: (1) It will be recognised across borders. (2) It enables you to securely present and share a wide range of attestations (like education diplomas, and train tickets). (3) It allows you to log on to a range of private sector services while preserving your privacy.