Goju Ryu which is an authentic Okinawan Karate has sticky hands. exhibit A. As a mainstream flavor or brand of Karate, it may not be as widespread as Shotokan... but it shows that something besides WC utilizes Sticky Hands. Which responds your question about "why don't arts like Muay Thai, Boxing, Wrestling or Jujutsu (all arts that have proven themselves effective in sport and street fighting) adopt the method?" Now, not all brands karate is created or practiced equally but Goju has been used in the streets for self defense, and some number of gojuka have competed in the All Okinawa Full Contact and done quite well. A good breakdown of the sticky hands in Karate... found here. Ryukyu Martial Arts: Crossing Hands in Okinawan Martial Arts And here is a screenshot showing Kyokushin guys in Brazil practicing Kakie or pushing/sticking hands... which is a brand of karate that is no joke.