Ask HN: Is Fingerprint Authentication in phones a good idea?

Why is Fingerprint Authentication a good idea? I never understood why?

What if a Fingerprint Phisher app acquired a young adult's fingerprint when he/she was young and stupid? How can that young adult change his/her fingerprint so it cannot be used once he/she grow up to be a rich professional?

I never I understood what is good news in this.

http://mashable.com/2015/05/22/android-m-fingerprint-authentication/