Creating a thin skin of elements on a model of solids is sometimes useful for durability analysis, both to run fatigue analysis only on the surface of a body and/or to put the stress tensors into a local element coordinate system, in the case of rigid body rotations.

For instance if you use fe-safe/Rubber the Surface algorithm is by default going to require analysis at the surface, and these membranes enforce the plane stress condition required by the algorithm. Or if you have a very large engine model, requesting Field Output at just the membranes will reduce the size of your ODB file and analyzing just the centroid of each membrane will speed up analysis in fe-safe without requiring any averaging. 

See this short video on how it's done in Abaqus CAE: