Because taiwanese follow the old traditional way chinese people used long time ago..while the use and invention of pinyin is to enable foreigners to understand and read the chinese characters. So i can say zhuyin is a lot more accurate than pinyin..taiwan uses the traditional characters same as what hong kong do while most of the population in china uses simplified chinese as well as pinyin ㄅ, ㄆ, ㄇ, ㄈ ㄉ, ㄊ, ㄋ, ㄌ ㄍ, ㄎ, ㄏ ㄐ, ㄑ, ㄒ ㄓ, ㄔ, ㄕ, ㄖ ㄗ, ㄘ, ㄙ ㄚ, ㄛ, ㄜ, ㄝ ㄞ, ㄟ, ㄠ, ㄡ ㄢ, ㄣ, ㄤ, ㄥ ㄦ, 一, ㄨ, ㄩ

At the moment, Taiwanese use the traditional characters because of the historical reason. It had to ascend to the beginning of the 19Th century when the PRC have not set up .Some enlighented clerisies propaganded the new culture and in order to make more people understand those artical, they appealed to simplify those words and made them easy to be read and written.This proposal was adopted and was carryied out for many years until now. But with the changes of situation, Mr.Jiang took his troops went to Taiwan island and they kept on the traditional characters while in mainland the simplify movement went on. That's why Taiwan and mainland use different chanracters. Although Taiwan and mainland use different characters, all chinese people can read between the two characters.Maybe it is difficult for mainland citizens to write in the traditional way ,but many of them can read fluently. in the 17Th people's congress, some one proposes that we should change the simplified character to traditinal one in the following 10 years with the purpose of protecting the traditional character as an immaterial heritage. Whether we will adopt this proposal or not, i think, it would not make obstacles in the communicatin betwwen both sides.

I agree with what Candice said about zhuyin. Besides, pinyin just makes no sense for Taiwanese. It is very hard for a Taiwanese to learn to spell characters with pinyin (my friend had tried. She never succeed.) As for the "simplified characters" question, each Chinese character is based on certain making rules, which we call 六書. And Chinese government adopted simplified characters because this way, people would be able to learn reading and writing more easily at a time when the literacy rate was still quite low. But traditional Chinese literature are all written in Traditional characters. Therefore it sometimes causes problems if one who learned Simplified Characters first wants to study traditional Chinese literature later. Although Simplified Characters are easier to learn, they can't present the beauty of many Chinese literature properly (as well as calligraphy, for example). That's why we are used to Traditional Characters. However, some youngsters do tend to use some Simplified Characters nowadays, such as 体 for 體, 囯 for國 . ( this trend is deemed inappropriate by the elders.)

taiwanese do use "pinyin"andTraditional Characters . we just do not use pinyin when typing cos it' s hard to understand

My online Taiwanese friends explained your question to me in this way. If you want to be able to use the English keyboard to type Chinese, then Hanyu Pinyin is the easiest way. If you want a dictionary in which you can look up words very quickly based on how they sound, without memorizing the bopomofo order, then if you should learn Hanyu Pinyin If you want to be able to write the sounds of Chinese in a way that the majority of foreigners worldwide learning Chinese can understand, for example if you have a language exchange partner in Taiwan, then yes, Pinyin is the best, but it depends on which system that particular foreigner knows.Globally most learn Hanyu Pinyin, but some who've only studied in Taiwan only know bopomofo. If you want to be able to write the sounds of Chinese on street signs and buildings so that most foreigners who've studied some Chinese can read them, then Hanyu Pinyin is the best way. If Taiwan doesn't have any of these goals, then Pinyin is not that important for the Taiwanese people.