Especially if you use the auto pilot, you should be clipped on.....Yeah it just seems over kill for a day sailor in the bay to have jack lines and tether. But i will be more careful with the auto pilot.
You don't need to rig jacklines.... just clip on to a solid point on the windward side of the boat. The shrouds are good if you have to go to the mast to reef. I never rig jacklines unless I'm on a trip. I just have secure points around the boat that allow me to leave the cockpit if I have to.... I always stay clipped on in the cockpit too.... to a windward padeye or jib car....
Let me ask you this.... if you're on a day sail, out in the middle of the lake a couple miles from shore with no other boats in sight... would you rather be floating in the cold water in your pfd trying to swim after the boat.... or would you rather be on the boat?
Like PFD's......... a harness and tether is useless unless you're wearing it.