SafetyNet and "authenticating the platform" is used for remote attestation, so app authors can deny phones access to apps and services if they're running root/k

SafetyNet and "authenticating the platform" is used for remote attestation, so app authors can deny phones access to apps and services if they're running root/kernel-level CPU code chosen by the user (or also an attacker without access to the phone's OS signing keys) rather than by the phone's manufacturer.