I really don't think that the 5.6's are a grade that shines. High E has one great pitch with some not so great climbing before it. Madame G's is ok, Shockelys is way overrated as a climbing experience. There are many far more interesting 5.8 and 5.9 climbs in the Gunks than 5.6. I think that the 5.6's are so popular and reverred since they are more attainable by more people.
I agree with you that I think its the attainable factor that makes them revered, but given the .10's in the Gunks, I think the .8's and .9's are just ok, but a greater percentage of people climb them then the .10's.... but I think that they are all easily attainable by the average climber