It's true, you don't need to do RC's in a dream to become lucid - but it's important to keep doing them during waking hours to sharpen your awareness. They're kind of symbolic in a way - it's use a symbol that you're really thinking about your state of consciousness and questioning whether you're awake or dreaming. If you don't so this enough while awake then you're less likely to achieve liquidity. So be sure to keep up the daytime practice. Then doing RCs to confirm you're dreaming when you think you are will add to your awareness in a dream when you do find yourself lucid.