Simply because the law was written that way. But also the whole idea of identity verification becomes pretty useless, if there is no chain of trust. You could run a modified client that lets you assume any identity you choose, exactly the opposite of what eIDAS is trying to achieve.
But you can run modified client already.
Rooted, wildly insecure devices can pass the attestation easily: https://magisk.dev/modules/play-integrity-fix-inject/
Safe, updated devices cannot unless they permit Google to run their surveillance services in the privileged, unconstrained mode.
Who wrote that law and why, this is the question.
I think we need some fingerpointing that EU officials strive to avoid.
It will likely display something like a QR Code with signature anyways, otherwise it's just a glorified passport picture?
Authorities/anyone could verify that it's not counterfeit. And photo should be checked anyways to match the person.
So I also don't see the need for attestation. For ID check it should be ok without. For signing stuff ofc it is not resistant to copying. But EID smartcard function already exists.
> You could run a modified client that lets you assume any identity you choose
Provided you know the secret key to a government-issued certificate. Making it impossible to copy said certificate is not really a requirement for identity verification.