Our architect spec'ed it under the floor of our screened porch floor when we designed/built it. We have an unusual wet-space over dry-space situation (screened porch on top of garage) - they laid down the rubber membrane, glued along the seams, between the sub-floor and floating stretchers that hold the T&G floor. If water comes through the porch floor, it runs off the rubber (floor has a 3deg slope, IIRC) and in-between the stick-built walls and the brick facade, then out through weep-holes in the facade.
Dunno if it would give you any shock-absorption through a wood floor, but if sealed along the joints, it will make a moisture barrier. I would think that plastic sheeting would last longer, though.