OP - You have not provided your location and Uber closely guards the locations where it will make the offer. There is no broad-based offer.
It is offered in specific markets, on specific terms and for specific services. It is also clearly a significant loss leader. Once you are used to routine use because it is dirt cheap, e.g. $6 for a $25 ride, the theory is that you will pay $25 for the $25 ride.