There are conflicting theories about whether or not it's a good idea to work with your significant other when you're making a film. As we've seen with Marilyn Monroe, if it goes wrong, it can put undue strain on your relationship. Maybe that was a key factor in Bruce Willis' thinking when he decided to pass on a lead role in 'Ghost.' If he'd taken it on, it would have been him who'd had the iconic 'let's make pottery sexy' scene with Demi Moore - who was, at the time, his wife.
We'll never be sure why Willis said no, but perhaps he was concerned about stepping too far away from his comfort zone at the time. He was an action movie star, and he wouldn't accept a more subdued role until he appeared in 'The Sixth Sense' years later. He also wasn't the only big name to turn 'Ghost' down; both Tom Hanks and Tom Cruise didn't see the merit in the script, and rejected the offer as well. Patrick Swayze had no such concerns, and was wearing a big smile when he movie collected the 'Best Original Screenplay' Oscar.