One reason is that it would be difficult to know which form of the word we would use in more logical spelling.
For me, 'one' has the same vowel sound as 'gun', for my northern friends, it doesn't.
My northern friends use different vowels in 'pat' and 'path'; I use the same vowel in each word.
Americans and British people pronounce some herbs (including oregano and basil) , and hundreds of other words, differently. Which form are we going to use in writing?
I could come up with many such problems, but I have made my point.

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