Kind of similar to the reason you'd wet a suction cup before using it: the water helps plug any small air gaps. But in this version, a fan spins the water and a

Kind of similar to the reason you'd wet a suction cup before using it: the water helps plug any small air gaps. But in this version, a fan spins the water and air inside the cup, with the heavier water being forced to the edge, and any water leakage being replaced from a reservoir.