In many languages that don’t use the latin alphabet (a, b, c, ect…) words are often written romanized so people not familiar with that script can understand. For example, in Japanese with word for thank you is ありがとう. It is romanized like arigato and pronouned ah-ree-gag-toh. However in Chinese, the word for that you is 谢谢 and is romanized as Xie Xie. It’s pronouned Shay-Shay. Another example is the word that’s romanized as Qing is pronounced “Shing”. Why is this? Why isn’t 谢谢 romanized as Shay Shay. Why isn’t Qing written as Shing?
It’s a foreign mispronunciation. Xie is pronounced “see-eh”, but just one syllable. Qing is not pronounced “Shing” either. Like another comment mentioned, once you get used to pinyin (characters written romanized), you’d be able to read pinyin easily. It’s like Romaji (for Japanese), for instance “to” is pronounced as such instead of reading it like English.
Cause there wasn’t one person that made up the systems. Some systems were made by Brits. Others by Dutch. Others by Portuguese etc etc. These systems were created decades or hundred years apart.
It’s called pinyin and it was developed in the 50s by linguists for the Chinese government. The pronunciation of Roman letters varies even among languages that use it natively. Think about John vs Juan. Same letter differnt pronunciation. You just have to learn the correct sounds for the letters in pinyin and it makes sense.