Cycling shoes and cleats do not magically make one go substantially faster, but they help one get to that goal. The explanation is in post #20 in this thread, as well as in several other posts by other people. Try reading the whole thread.

Others on this thread have argued that they can apply good technique without a cleated pedal, and well, bully for them, but for many of us, so-called clipless pedals are a significant aid in development of good pedaling technique.