>>8
For Japanese it would be stupid, there's very few different sounds in the language that all words would end up being the same. Take the word "e" for example (very basic one), you probably have hundreds of different words that are spelled that way, can you figure out without context what it means?
On the other hand, if you start doing: 柄, 江, 画, etc... then it all makes sense.
Korean were using those characters before, called Hanja, until someone really smart invented hangul, which is considered the most logical and intelligent way of writing today.
What you say is like saying French or Spanish should use only the 26 letters of the alphabet, without any change to them, it doesn't work like that. English speakers should be happy to only have 26 letters.