I know a story about a pilot who thought he would take a plane when the eng told him it need some more checks. The plane was loaded and ready to depart other than one final check, the eng told the pilot what was happening but while the eng was back in the libary the pilot had the doors closed and pushed back and tried to go flying. The eng made a phone call to the tower and told them what had happened the a/c was then refused permission to take off and ordered back to the terminal. The pilot tried to argue that he was happy with the a/c so it was OK but no dice the tower refused him.
I could list many other examples of pilots being told they cant go when they want to and pilots refusing planes engineers have ofered them. its something that goes both ways we double check each other for departures its a fail safe system we both can stop an a/c from departing its the safe way.
Unfortunatly a pilots view often changes depending on the destination hes going to or if his friends are on staff travel. After all we are all human thats why we have the systems there.