You're referring to a perfect sim, which probably won't be possible for a while, but they're close enough right now and are being used to treat a variety of phobias and other mental health problems. So it's getting there and is already useful for sure. Being used for education as well as the obvious entertainment apps.

Once bandwidth inevitably increases and it is a perfect simulation it'll change life as we know it. The virtual life will be way better than real life, which will become mundane, boring and depressing.