First of all, how can you be so sure of that, Nikotine? Have you ever tried to write a song?

Second, I don't recall ever hearing Miley use auto-tune yet, but even if she did, no talented singer uses auto-tune all the time. They might use it to add some sort of audiovisual special effects, but that's about it. I'm sure you can tell when a singer is using auto-tune and when they're just using their regular voice, because when one is using auto-tune, you can hear some sort of special effect in their voice.