Our pool has one return and one skimmer. Our return has never had an "eyeball" or any other sort of restricting device to focus water flow, just an open threaded pipe fitting. It was that way when we bought the house, and I didn't know any better.

What am I missing by not having an "eyeball"? Is it something I really need? Circulation seems adequate, stuff like leaves and other floating debris always end up in the skimmer.