You're looking at this from the perspective of an educated end user. You're pretty secure already from some common attack vectors. You're also in the minority. Passkeys are largely about the health of the entire ecosystem. Not only do they protect against credentials being stolen, they also protect against phishing attacks because identity verification is built in. That is of huge value if you're administering a site. Yes if everyone used a password manager there would be less value, but only about a third of users do that. And as an admin you can't just say "well that guy got phished but it's his own fault for not using a password manager."