Why not indeed. You're chess opponent mades a good move. You travel forward in time to see what his next move is going to be so you can counter it before it happens.
Your favorite NASCAR driver loses in a close finish with the winner. You travel back in time and sabotage the winner's car.
You really wish Foreman had beaten Ali. So, you travel back in time with the video tape of the bout, show it to Foreman before the fight and let him adjust his strategy accordingly.
One could think of a zillion examples where games of skill could be foiled by time travel. Imagine the possibilities in poker!