I know one reason is because RJ's will often land 11 at EWR, and will come over SBJ at about 3000 to join final.
We recently had a vistor to the glider operation whose a captain at XJet. He says when they come through that area they're totally heads down and not paying a bit of attention out the windows.
No good pilot, let alone a captain at a 121 carrier on a turbojet aircraft, should allow both pilots to be heads down at 3000 feet.