When you are fishing that shallow, fish can pick up on your presense by noise, site or vibration. So its our instinct to cast away from our domain.
IF we are in a boat, than we feel better about casting close to shore. If we are on the shore, than we cast out deeper, because more than likely the fish closer to us have picked up on our presense.
Plus in a boat, you can cover more shore without disturbing its surroundings. If you were on foot, walking, talking, or any type of movement will most likley be noticed by anything that close, so we naturally look to fish deeper, and further away from where we stand. This is why i stress to people to lay off the trolling motors. Its best to use the wind and drift down a shore, than to drive urself up and down a shore. If you get a good wind, u can fish an entire cove in total stealth mode.
This might not be absolute in all cases, but it sounds good lol