To learn the choreography. The first and most obvious reason to rehearse is to learn the choreography. This means learning the steps, the timing, and the formations. It takes time and practice to get these things right, and rehearsing allows you to perfect your performance.
To build muscle memory. When you rehearse, you are not only learning the choreography, you are also building muscle memory. This means that your body will eventually be able to move through the steps without you having to think about them. This is important for performances, when you need to be able to focus on your performance and not on the steps.
To develop stamina. Dancing is a physical activity, and it takes stamina to perform a dance routine. Rehearsing allows you to build up your stamina so that you can perform your routine without getting tired.
To perfect your performance. Rehearsing allows you to perfect your performance by practicing your timing, your movements, and your expression. The more you rehearse, the better your performance will be.
To build confidence. Performing a dance in front of an audience can be nerve-wracking, but rehearsing can help you to build confidence. The more you rehearse, the more comfortable you will become with the choreography and the better you will be at performing it.
Overall, rehearsing for a dance is essential for learning the choreography, building muscle memory, developing stamina, perfecting your performance, and building confidence. If you want to give a great performance, you need to put in the time and effort to rehearse.