Do you trust computers?
Not a good idea - the time you really want two pilots is when something goes wrong, such as your FMC doing strange things (QANTAS A330 over the Pacific?) where you definitely want to get the electronics as much out of the loop as possible. If you're on a long cargo flight, on your own, who's going to keep you awake and alert? At least if there's two in the cockpit you have some degree of redundancy if one pilot is incapacitated. Indeed, there are some accidents where it was considered that with a flight engineer in the cockpit as well, the accident would never have happened.
Imagine the fun to be had by successfully hacking into the data link, your very own remote control aircraft, full-size.