So there is no direct relation between fighting and patterns other than patterns help in execution of techniques (because of the over exaggeration of motion). Basically, forms are a way of persevering the past. I guess they could also be seen as a form of moving mediation. Do you feel the mastery of forms are absolutely necessary in being able to spar and defend ones self? Could TKD exist without forms?
Forms training is not necessary for one to be able to spar or fight or defend ones self. For example, look at boxers, wrestlers, UFC fighters, street fighters, soldiers, etc. They are not concerned with forms at all.
Could Taekwondo exist without forms? Yes and no. Many students would be overjoyed if forms training disappeared and they could just spar all the time. If forms were not used, some other type of training methods could be used to replace it, so Taekwondo as a fighting system could exist without forms.
However, Taekwondo is a martial art. Without the art provided by the forms, the martial art of Taekwondo would cease to exist.