For sure they probably don't find the salt on the skin unpleasant, but ya gotta go back to the wolf on this one. Wolf pups greet the adults with licking as a sign of submissiveness usually around the mouth. My previous Daisy dog had this almost artistic knack of giving strangers a smooch right across the mouth. She'd nail em if they were with in a short jumping range. Her weight was 74 lbs, not too small.

Of my two current puppies, Clover 65-70 lbs the larger is more reserved, but that's just her nature. If given a chance however she is definitely into licking ears. Whereas Barney the smaller of the two at 55 lbs is a licking machine that starts on the fingers, or arm, and heads for the face. He is also a lot more hyper in energy level. While typing this he attacked me with his licking. Cause: He wants his piece of rawhide to chew on.

My speculation on the licking is that possibly the smaller the dog, the more they feel obligated to be submissive around us.