Shag carpeting is an amazing idea. 
Apparently in the late 50's and early 60's, those clever guys at DuPont found that their new polyester fibers could be made into carpeting; and more than that, since their new fibers were so different and miraculous, you could make extremely high pile, shaggy cut carpeting, and it wouldn't become matted into a disgusting mess of plastic fiber, dust, shed hair, dead skin and spilled drinks. 
So that's how they sold it to a thankful public. 
And, naturally, shag carpeting proved to almost instantly become matted into a disgusting mess of plastic fiber, dust, shed hair, dead skin and spilled drinks.
Simply amazing.