Possibility of pilots getting distracted inside the cockpit exists too. Has happened in the past. You just get obsessed with the problem and then no one is flying the aircraft, you wake up when the ATC calls you in for the final or changes the runway. You realize its too late to get the stuff in, and you choose to go visual. 99% of the time, nothing happens you land (heavy, hot/high, etc. etc.), and talk about the problem on the tarmac, and go back to your next sector.