When your feet are on the floor, you can transmit force. When they’re off the ground, you can’t.
Almost every reader will have immediately thought, ‘That’s not true! How do you explain the flying knee / jumping kick / superman punch?’
I call this one a rule because it can be effectively broken. While it’s illegal for the feet to leave the canvas in boxing, both jumping and using the legs as counterweights are very effective means of feinting, as well as generating and manipulating momentum to strike in other rule sets.
What’s important to remember is that when your feet are on the floor, you can drive the rotation of your torso through your legs for consistently powerful striking. You can also move away immediately after. The more you move, the more difficult you are to hit.
It’s no cliché that good boxers make good dancers and vice versa. Footwork is essentially the means by which one opponent controls the rhythm and timing of the engagement.
While you may be moving away from your opponent, if you can control when and where, you’re demonstrating another form of dominance and so long as you’re engaging, you’ll score points with the judges.
The essence of competition is control.