Fingerprint-recognition is a password that you leave a copy of on everything you touch.
True, but of course it is sensible to relate the level of security to the importance of what is being secured.
You would be foolish to secure a bank vault with TouchID. It is quite sensible to use it on a phone though as it would take a reasonable amount of effort to break the protection for probably minimal payoff, bearing in mind physical possession of the phone is a further protection so if you lose or someone steals your phone you can take appropriate measures.
It’s also a great help for older people or those who struggle with passwords, etc.