My dad didn't like iCloud Passwords because he still uses a Windows laptop and only recently has the iCloud Passwords app been good or all that useful. We settled on 1Password a few years ago and having 1Password on his phone and setup as his default password app means that iOS uses it as the default Passkey app as well. "It just works."

The vendors could use it to enhance lock in, but for the most part the vendors all seem in agreement that the rising tide safety to float all boats of Passkeys is worth investing in making them friendly, especially to non-technical users, and to some extent try to avoid direct lock-in.