For repetition

1. To improve your ability to perform that task. The more you do the same thing, the easier it will become.
2. In order to memorize something. Reading the same portion of a book or reciting pieces of a speech can help you to commit them to memory.
3. So that when a moment comes that you don't have time to think, you'll already know what to do and react accordingly.
4. So that you'll be able to cook something the exact same way. The more you use a particular recipe, the less you may need to actually follow the written recipe.
5. In order to build or break a habit. Habits need both consistency of action and time.
6. So that you'll be able to play your part on a team. When you are part of a team, everyone needs to know what their part is, and how their part blends with the parts of everyone else. That's one reason why teams gather for "practice".
7. In order to form a resonance. Be it in music, film, literature, or some other format, resonance is a powerful tool that your audience will respond to when it is used correctly.
8. Repetition is an excellent way of confirming an experiment's result.
9. As a way to focus your thoughts. Repeating yourself can on occasion help you figure out what step to take next on a project.
10. Sometimes doing something again and again can simply be fun.