Fixed it for you
"The [fingerprint] scanners improve smartphone security by giving users a second, physical authentication method on top of their existing login passwords, PINs, or gestures."
"The scanners improve smartphone security by giving users a way to unlock their phones that's convenient enough that they will use that instead of having no PIN/password/etc. at all."
It's annoying that 9 months after the iPhone 5S was released, there are still people who think that fingerprint scanners exist to provide a Tom Cruise, Mission: Impossible level of security and attack it on that basis, whereas the scanners are clearly a convenience feature.