By locking the strings close to the head of the guitar combined with an advanced tremolo mechanism, detuning of strings as an effect of using the tremolo arm (whammy bar) becomes much less likely.
Many modern electric guitar players (Joe Satriani, Steve Vai, ...) make heavy use of this and excessively use the whammy bar to generate new sounds that were not practical to achieve with traditional (vintage) tremolo systems (such as the ones used for example on Fender Stratocaster guitars).