The purpose of lucid dreaming in dream yoga is to find freedom and flexibility of mind. This is done so that you are not taking yourself or your life with whatever challenges you are facing so seriously. You will deal with your life but you will be doing it lighthearted.
Flexibility of the mind is developed after you become lucid. It is done by doing the magic stuff you can in a dream. You can transform the dream or yourself in any way. You can fly and meet wise dream characters or have experiences that broaden your mind and experience from limited, self centered point of you, towards more encompassing presence.
So do whatever you love to do learning about yourself and your limitations to grow towards more peaceful and joyful presence you can share with others in your unique way. Have you ever wondered how it feels like to be a buddha, awakened, free or the enlightened one? It feels just like you, only without any grasping or resisting to any situation in life. Dream yoga can help you to grow towards it so that you can share your peace and joy of being with others.