Because, you might play players, or make substitutions, in that particular game that you might not make otherwise.
You might bring in a hot pitcher that is normally scheduled for the next game.
Or sandbag the prior games to increase the odds in the game your betting on in order to increase the winnings.
Why would you do that????????? You play to win! And if you have no money on the game, there is absolutely no reason to lose...............
And if you start doing things that seem suspicious, play a pitcher out of order (c'mon, not gonna happen), you're gonna get busted.........