Soccer agility with the ball is essential to be a successful soccer player. Once we have the ball we need to be able to move it around, to move, to dribble, to pass it. But it's not the skill with the ball that you have. It's the position you get yourself into before you actually have to make those positions with the ball.
It is the movement with the ball. It is moving around, moving along the sideline without losing track. Not zigzagging but staying on the line, having one leg always on the ball, moving forward, dribbling, making corrections with the ball without falling over. Moving sideways, being able to make the moves, being able to make the quick cuts, being able to make quick decisions. Changing rhythm, making a fake move, speeding up afterwards. Those are many tiny steps, many tiny processes that happen inside your body that make you able to perform those moves.
And this is, as I said, it's change of rhythm. It's deceiving your opponent. You will not be able to deceive your opponent if you are not able to quickly shift your body weight from one side to the other. You make the decision, your body will react on it. But to speed things up, practicing soccer agility is essential.