Wouldn’t it be great if every letter in English spelling only made one sound? Why can’t our language be more “phonetic” like Spanish? Well it could be, but in some respects it is “too late,” and in any case our way has its perks.
To briefly make my point, here are a few practical obstacles for creating a 1:1 sound:letter script for English.
(1) Transparency of word roots is valuable. “Insane” and “insanity” have such related meanings that spelling them differently to account for pronunciation would be confusing. As another example, the silent /n/ at the end of “column, autumn, condemn” is worth keeping since it gives rise to “columnist, autumnal, condemnation.”
(2) Different spellings are helpful for reading homophones, which are common in English (though not as common as in Chinese, which needs much more meaning-specific morphemes). E.g., “eye” vs “I,” “you” vs “ewe,” “two” vs “too” vs “to.”
(3) Spelling should not reflect nuances of pronunciation that most people do not notice, such as coarticulation, assimilation, resyllabification, which change the pronunciation of words depending on spoken context. “Cap driver” would be confusing even though we only imagine pronouncing the “b” sound most of the time. Same goes for “apsurd” and for foreign accents (“do you vant some beer?”).
These ideas aren’t mine–I got them mostly from Stanislas Dehaene’s “Reading in the Brain.” It’s a cool book!