Did you know that English is one of the most difficult languages in the world in terms of its spelling system? (I'm sure you do.) Well the main reason for this is that it's not very phonetic. There are historical factors which explain this chaotic spelling system. Here are some which you may care to research: the great vowel shift (around 1400), carelessness in copying manuscripts, Norman spellings for anglosaxon words, Claxton standardization, the Latin Language etc.