Why 3 phase motor rotate in opposite direction?

You would reverse rotation on a 3 phase motor to get it to run backwards. Say I fill up a tank truck from a lake. I turn on my generator. I run the motor in one direction. Then I drive the tank truck and the motor to a different location. Then I turn on my generator. I attach the hose to the motor on tank truck. I throw the switch to make the motor run backwards. I aim the hose at the fire in your house. Aren't you glad that I can make my 3 phase motor run backwards?