The ability to quickly turn off the phone is useful when you need to activate a long password so that you cannot be forced to use your fingerprint to unlock it.
The only place where you would not want to use biometrics are western* countries which would allow the police to compel you to give out your fingerprints to unlock the phone.
With the exception of the UK in which not giving out a password or decryption key in the course of an investigation even if you are not the suspect of a crime can land you 7 years in prison these days.