A mother teaching her daughter how to cook a ham, cuts off both ends of the ham before placing it in the oven. The daughter ask the mother why she does that. The mother replies that she didn't know why, that's just the way her mother did it. So the daughter goes to the grandmother and asks her, why she cut off the ends of the ham. The grandmother replies, she had a small pan.
In Kung Fu in is important not to mimic movements mindlessly. Understanding the greater intention of the movements, the various ways it can be used, and the details in it's execution are necessary for achieving the full potential contained in the technique. Otherwise it is likely that you will not be able to apply the technique effectively. Those who only practice forms often fall into this trap when they neglect to practice the application of the techniques contained within.
This is why it is important to train with a teacher who knows why he practices the way he does. And to train with many different teachers who will give you various perspectives, and place emphasis on different areas. No teacher can know everything, and some are even unwilling to convey every detail.
"Knowing others is intelligence; knowing yourself is true wisdom. Mastering others is strength; mastering yourself is true power." - Tao Te Ching