an useless question, sorry for saying that, then do you know why korean use korean, japanese use japanese...and so on okay, to be seriously, i do believe that hanzi is called hanzi, just cuz chinese use it, and that is all and just cuz there are so many devisity language which make the world so interesting

because chinese has a lot of characters that share the same pronunciation but have various meanings, if we use alphabet we cannot understand many of them properly. and china has many dialects, some r impossible for people from other place to understand, but we use the same hanzi, so it helps people in different places to communicate, it also helps us to stay together as one country. here's a good example for why we cannot use alphabet, try to read this, the famous "Lion-Eating Poet in the Stone Den" by linguists Yuen Ren Chao in the 1930s'. http://en.wikipedia.org/wiki/Lion-Eating_Poet_in_the_Stone_Den

Many different characters have the same pinyin. Sometimes without context you cannot judge the meaning of a chinese sentence only from latin alphabet.

Pengyou , are you interested in Chinese ? If so,you should know that hanzi is made up by bihua,just like English is made up by latin alphabet.That is to say ,maybe your question has no answer,or what I said just now is the best answer.