‘Why don’t you write it how you pronounce it?’
*sāriġ is the Old English spelling of ‘sorry’ before the shortening of the root vowel during the Great Vowel Shift
My students often get intrigued, confused, and/or annoyed by English spelling. The reasons are many. I usually chicken out and say: ‘Sorry! I didn’t invent it!’
Most languages have a much more highly phonemic orthography than English. That is to say: in most languages, you can largely tell how to pronounce something from the way that it’s spelled or written – often to the point that there is in fact no word in that language for ‘to spell’. This is why this question is unique to students of English as opposed to other languages.
English, as we know, is different. When I don’t chicken out, I often refer students to the Great Vowel Shift in the Middle Ages. English orthography was being standardised in the same period in which the language was going through a huge multi-generational shift in vowel pronunciation. This resulted in all sorts of different ways to spell similar sounds.
To all students (and natives): This great animated video provides a much fuller answer.
This video is by Arika Orient, who makes videos for Mental Floss. Lots more great videos about language can be found on her YouTube channel.