Toilets
So what happens if the pilot needs the toilet? will he just leave the plane to fly itself? do you really trust that? i sure as hell don't.
And anyway i agree with the many other posters that having one pilot would be bad for the economy by taking away jobs, moral of crews on long flights and the safety on board the aircraft.
so i say single pilot aircrafts have no place in aviation because pc's make errors and there are many more errors on a PC than in a human mind