The same way people who don’t use 2FA access sites that require 2FA - they don’t.
Not that this is an actual concern since Chrome, Safari, Windows, iPhones, Android, Yubi, etc. are all alternative to password managers (which you should already be using in 2024 regardless) and all function with passkeys.
I also wasn’t suggesting forcing every user to not have a password (though I’m fine with that) but if YOU the passkey user can’t disable your password then the passkey serves far less of a purpose and you’re still completely phishable.