Orthography
The other reason that alphabets never exactly fit languages is dialect. A spoken language varies from place to place and from time to time. This is very obvious with English, as the pronunciation is so different in different parts of the world. A written language will always be less flexible than its spoken parent. It has a different function, and is produced mechanically. It must serve everyone who speaks the language, and it does this by keeping the spelling similar from one time to another.