What about the fact that fingerprints make great usernames but trash passwords?
Perhaps the poor security and extra hardware and software are enough to discourage makers, they can add a variant with a FPS and if that doesn't sell at all they won't make many others.
Right. Fingerprint is something you are. Can’t be changed. Same for any biometric.
Useful as one part of a multiple factor authentication scheme at best but never on its own. Not to mention there are cases in the US where you can be compelled, forcibly if needed, to unlock a phone. But compelling you to “say” what your password may be covered under fifth amendment protections.
This is why I only use biometrics for website passwords and the App Store on my Apple devices. To unlock requires a password, which cannot be forced (though at least one judge kept a man in jail for contempt of court for not unlocking a device, which should be illegal under the fifth imo).