10. A slight miscalculation by team staff on the “driver weight vs. horsepower” ratio for the backup car.
9. Been there, done that; didn’t want to relive the demanding schedule that being the reigning champion entails.
8. Put off redecorating his master bedroom one too many weeks.
7. Poor scheduling of the annual “Joe Gibbs Racing Prank Race,” when the No. 18 team has been known to secretly switch cars with the No. 20.
6. Wanted to make sure someone else got their turn at beating Jimmie Johnson for the championship.
5. Found out the top-10 guys were going to be on the Late Show with David Letterman, and wanted to be on the Tonight Show with Leno instead.
4. Team orders: Back off so Denny Hamlin has a chance.
3. Thought the “past champion’s provisional” meant he was already in.
1. No one fully explained to Tony Stewart that “backup car” was just an expression.