I am currently not trying to quit drinking (although I probably should). I enjoy alcohol free beer. Sometimes I want to drink a beer and I don't want any alcohol. As simple as that.
If someone is trying to overcome a bad drinking habit, I can imagine "fake alcohol" drinks can be a useful help. Use to drink beers everyday? Replace all of them by alcohol free ones, then when you are craving for a beer, you get one of those from your fridge and you avoid going out and get a alcoholic one.