Now, if you arguee that no thief will ever want your data (and you'd be probably right), it doesn't matter if you lock your phone or not, and it won't matter how you do that. In this case, locking schemes are completely useless.
(Now, I'd be content with a fingerprint reader that recognizes a finger - any finger - and unlocks the phone. It's enough protection if my pocket can't defeat it. Unlocking only by specific fingerprints looks like a pain, nobody else will be able to unlock my phone? Thanks, but I'll pass that.)