

When English-speaking kids are taught to read, and to spell, it’s very much an out-loud process, using phonics, and methodically covers the various pronunciation of all the letters’ sounds. “Sound it out” is the first step in decoding written words. Then of course there’s using context clues to figure out what word you’ve heard before could be spelled using those letters’ possible sounds. And it’s not until later, once all the common rules and exceptions of pronunciation are automatic, that you start “reading to learn” and attempt words you’ve never heard before.
Most adults I know who study a foreign language do so in order to speak it, perhaps visit that country. In languages that build words from letters, the phonemes are important to meaning. Obviously “heresy” is very different from “hearsay,” but sow and sow are different words that sound different, while sew and so are also different but sound the same. It’s especially important in order to appreciate literature, poetry, music, and jokes.