Because Japanese characters have no direct relation to Chinese phonetics. Both belong to different dialect continuums, phonetics aren't compatible.
And I suspect same might explain lack of native Chinese phonetic script; `Chinese` isn't a single spoken language, but what is called as such is its Beijing area version of one of Chinese(or Sinitic) languages. The written language was universally understood in China due to bureaucratic needs, but AIUI it's not same as spoken language and it's not necessarily used everywhere. Maybe they just had little uses for a standardized phonetic script?
It is still very useful to standardize the pronunciations, since people with different dialects had to meet especially those officials in government. There was “yayan” for this purpose.
Because Japanese characters have no direct relation to Chinese phonetics. Both belong to different dialect continuums, phonetics aren't compatible.
And I suspect same might explain lack of native Chinese phonetic script; `Chinese` isn't a single spoken language, but what is called as such is its Beijing area version of one of Chinese(or Sinitic) languages. The written language was universally understood in China due to bureaucratic needs, but AIUI it's not same as spoken language and it's not necessarily used everywhere. Maybe they just had little uses for a standardized phonetic script?
1: https://en.wikipedia.org/wiki/List_of_varieties_of_Chinese