Well that's not as clear as you make it seem. Likelihood of getting caught is a very strong factor people consider when making to choice to commit a crime or not; much stronger than e.g. the severity of the punishment. What video surveillance does, is increase the solve rates, in other words the chance of getting caught. When this is internalized by criminals, it's not unlikely that crime rates will go down, i.e. that surveillance will have a deterring effect.

So it's true that putting up a camera doesn't deter by the fact of being there. What does deter is the pervasive cognition that you're always being watched. Whether that's a worthwhile trade-off is another question, but one for which the debate is much harder to win.