That's how writing used to work for the longest time. Each letter has a sound, and you write down the letters that match the sounds you make when pronouncing the word. Two people might not spell a word the same, so the only viable way to learn would be what is now apparently called phonics.

We only really started to standardize spelling in the 1500s. Which I guess means that by the 1800s English spelling and pronunciation had drifted far enough apart that phonics was a concept worth putting in words.

In most languages with alphabets the pronunciation of letters is consistent enough that the issue doesn't seem to come up a lot. Phonics is just the obvious way to do it in those cases