Who really knows how saucers work? You can't even truly tell if that's a legitimate picture.

A rotating spacecraft will produce the feeling of gravity on its inside hull. The rotation drives any object inside the spacecraft toward the hull, thereby giving the appearance of a gravitational pull directed outward. Often referred to as a centrifugal force, the "pull" is actually a manifestation of the objects inside the spacecraft attempting to travel in a straight line due to inertia.
The spacecraft's hull provides the centripetal force required for the objects to travel in a circle (if they continued in a straight line, they would leave the spacecraft's confines). Thus, the gravity felt by the objects is simply the reaction force of the object on the hull reacting to the centripetal force of the hull on the object, in accordance with Newton's Third Law.
. The hypothetical beings are perhaps trying to make themselves more comfortable gravitationally wherever they go.
An interesting idea!
Does this sound right? UFOs and the reason behind they're design