The original kwans taught patterns that were taken directly from Japanese and Okinawan karate styles (Shorin and Shorei). Because of conflicts with the Japanese and Chinese, Korean martial artists wanted to distance themselves from things related to Japan and China, including patterns. Although this attitude is understandable, the change has not been accepted by all Korean masters. When you remove the traditional karate patterns from Taekwondo, you remove its roots, its art, and its soul.
The International Taekwondo Federation (ITF) uses Chang Hon patterns (hyung) developed by General Choi in the 1950's. The patterns express much of the influence that karate had on Taekwondo. The founding members of the Korean Tae Kwon Do Association (KTA) agreed to favor none of the patterns of the participating schools, and instead to create an entirely new set of patterns to ensure agreement among the different schools. The KTA adopted the Palgwe and Taeguek patterns (poomse) on January 30, 1967, later the Palgwe patterns were discarded. Although the Taegeuk patterns were designed especially for Taekwondo, the karate training of the developers still found its way into the patterns. About fourty percent of the techniques in Taebek pattern comes from two Pinan (Heian) katas, nidan and sandan.
Modern Taekwondo has been changing patterns to reflect its competition techniques and emphasis on kicking. It may be expected that future pattern changes will continue reflect the increasing emphasis on the competition kicking aspects of Taekwondo. As Taekwondo continues to stray from its roots as a "martial" (combat) "art" (way of life), it may gain popularity as a sport, but it will continue to lose favor as a martial arts, just as Judo did in the late 1900's.