I thought this style of identity detection (using biometrics) was decided upon as a poor technique by the security community?
Once someone else has your fingerprint and a way to spoof it, there is no way to generate a new biometric.
Well, if hackers steal one of your fingerprints, just use a different finger.

You are generally correct, though. Biometrics are a poor method of security. What they are useful for is user identification. Like Janx mentioned, you could have the phone recognize the user and pull up their profile based on who pulls it up, like a user log in that doesn't require you to remember the user name. I used to work at a company that was implementing fingerprint identification for QA purposes (i.e. the system knows that Worker #23 built widget #294839). I ended up leaving that company before the implementation was successful, though.
The part that confuses me is the things that made fingerprinting useful there make it a pain in the butt for a phone. There are inevitably going to be times when it is *useful* to log in as someone else on a computer, and fingerprint access makes that hard. And the concept of user accounts is potentially useful on a shared computer, but phones tend to be single-user system. I really have no reason to set up a second user account for my wife. I suppose there may be times when it's useful for kids or emergency calls, but proper passwording and 911 access on home screens have already solved these problems.
Practically, using a fingerprint has a problem of use in an even slightly dirty environment, or with wearing gloves, or, say, what happens if you have a cut or burn.
Aside from wearing a bandage over a cut, this is less of an issue that you would think. A fingerprint scanner doesn't actually take a photo and compare direct images of your print to a previous image. At least, the one we used in manufacturing didn't. Instead, it processed the scan as a series of lines, and identified about 10 key locations: things like intersecting lines, centers of circles, etc. It then stored just the data for these points, and compared them to the same key points on any new scan. It could allow a couple of points to change (i.e. you have a small cut, one point is screwed up) and still pass the scan. Coloration or lighting wouldn't have any effect as long as there was sufficient contrast, and distortion of the image could be allowed as long as it was uniform in the right way (i.e. known smudging or scanning artifacts).
This method also removes the security risk of hackers (or the NSA) stealing your fingerprint for access elsewhere. Since the system didn't actually store an image of your fingerprint, there was no way to completely reconstruct it. A stolen data file could only be used to spoof your ID if it was used on an identical fingerprint ID system with identical settings.