Because people from other countries know that a player in China who is ranked 147 can easily beat a player ranked 28 from other country.
Players avoid CHINA master because they are always afraid of many CHN players in early rounds like up and coming like Tian Houwei and Xue Song. Meanwhile, JPN SS is more prestigious, they also can still compete in early rounds before they all succumb to LCW or Chen Long in the end.
if i am player,i will not forget what happen in CO 2007. since then the participation is getting lesser and lesser. in the end,the tournament is done for good.