Why the 127 encodings of ASCII needed to be extended to 256?
ASCII has 128 characters. Many countries had similar encodings for 128 characters. That is all history. Nobody uses ASCII anymore. There was a phase with lots of different encodings for more than 128 characters, some with 256 (Mac Roman and Windows 1152 were quite popular) and some like the Chinese GB with thousands of characters. 

Nowadays people mostly use Unicode, with a bit over a million code points, which can be further combined to produce more characters. There are plenty of unused code points which can be assigned values in the future, and that happens all the time. 

Please note that for most people English is a foreign language. And it would be “naïve” to think that ASCII let’s you write all English text.