Enough repetition gives you something to fall back on. Something that, unlike your primal instincts, you can shape up to be what you want it to be. You can decide that whenever confronted with a certain event, you will unravel a precise and optimized sequence of events. You choose these events and by repetition, make them your reaction. Over time, they become your reaction as much as anything else that's innate. Muscle memory and beyond. Such training "leaks out" in certain situations, often to your advantage.
Wing Chun is a skill for life.