For the Kids:
In soccer you are seldom on the field alone. There is usually a whole team of people looking to learn from the coach. There may even be other teams practicing nearby, parents waiting around on the sidelines, and lots of other people shouting and making noises. This can be a distraction. So it's important to listen for the coach's voice during practices and games.
It helps to show that you are listening. How can think you can show your coach you are listening to them?
Those who listen more to what the coach says, will to learn more about the game and are better players.
Coach's Corner - A few words about listening:
You tell the kids at the very beginning of your first practice that whenever you clap, they have clap the same number of times you clap. You clap twice, they clap twice. Make sure to also tell them that this is time for them to listen. You can usually get everybody’s attention after 2 to 3 sequences of claps and that only takes normally 3 to 5 seconds. Much better than yelling
Or consider picking a word, that when said, the kids stop and listen.
Give positive feedback when players listen.