It is (or was?) also fairly normal for British snooker and darts players to place an 'insurance bet', by betting on themselves losing a game (http://www.dailystar.co.uk/news/latest-news/144899/Steve-Dav...)

Say that the difference between winning and losing a final is £50k, and the bookmakers pay out even on a bet that you lose. If you bet £20k on you losing, you change a "nothing if I lose, £50k if I win" game into a "£20k if I lose, £30k if I win" game.

Some players prefer such a game. Placing that bet might even increase their chance of winning, as part of the stress gets removed from the game (you're playing for £10k, not for £50k)