However, it's often used in a more colloquial and sarcastic way, similar to English phrases like:
* "Where do you live, under a rock?"
* "Have you been living under a rock?"
This implies that the person you're speaking to is completely unaware of something that's common knowledge or has been widely discussed.
For example, if someone says "I think the Earth is flat," you might respond with "Mais tu vis ou ?" to express disbelief and imply they're out of touch with reality.