Only through sparring and interacting with your opponent will the student learn the techniques and gain the quick muscle memory required for Gumtoogi and Bongtoogi. In order to effectively spar without injury, one must have access to the proper armor and weapons.
Thousands of years ago, Koreans had to learn how to train for war without maiming each other in the process. Thus, they created the Jukdo (bamboo sword), Jang Bong (battan staff) and Hogu (armor). This allowed them to continue to prone their martial prowess without the worry or losing life or limb.
This remains true today. Gumtoogi requires the protection of wood and bamboo equipment during matches to keep the challengers safe from each others strikes. An Experienced Swordsman understands the importance of the protection the armor provides him.