Kakao in the global market context

Netmanias tech-blog published an excellent overview of the global growth in over the top (OTT) services and rich communications services (RCS).  As shown in the accompanying infographic showing monthly active users of leading OTT services (click for a full size version) , Kakao Talk, which is dominant in the South Korean market, has failed as yet to make a large dent in the global market.  According to the blog entry,"With the help of strong supports from domestic market, WeChat is becoming another worldwide OTT communication service platform. LINE, originated from Japan, is step-by-step penetrating into South East Asian market. KakaoTalk which dominated Korean market but has been staggering outside Korean market has merged with Daum, the second biggest portal service provider in Korea, seeking out further growth by gaining more contents strength in this battle."
After seeing this infographic and reading the Netmanias overview, I  learned that Line offers at Line-out service, so I promptly decided to install Line on my Galaxy 5 phone. (Remember that I stopped using Skype after Daesung Corporation began requiring use of Internet Explorer and Active-X controls to pay for Skype-out!)  While installing and setting up Line, I came to the realization that the main reason Kakao has had difficulty penetrating the global market is its lack of a high quality 1) English and 2)mobile friendly user interface.  This situation is reminiscent of other Korean services that have failed in the U.S. or global marketplace.  One example was Cyworld, which preceded Facebook by half a decade, but failed in its efforts to penetrate the U.S. market.   The lack of a world class English, mobile friendly app interface no doubt reflects not only language and a knowledge of mobile app creation, but also deeper cultural preferences.