Jamy Ian Swiss calls himself an “honest liar,” because as a magician, he promises to deceive his audience, and then promptly does. User interface designers are somewhat similar, though probably a bit less honest. We constantly lie to our users about what they actually see. A button on a screen isn’t really a button, it’s a bunch of colored dots. The better we lie to users, to more easily we can convince them that it actually is a button.
So while we may not be as honest as magicians, our lies nevertheless are in the user’s best interest.