English spelling wasn’t always so convoluted; there was much more rhyme and reason to Old and even Middle English. But the spoken language has evolved, as all languages are wont to do: Pronunciations have changed and foreign words have been introduced, sometimes retaining the spelling conventions of their original languages.
Written English has also evolved—but mostly in ways unrelated to the changes in the spoken language, thanks in part to shenanigans and human error. The first English printing press, in the 15th century, was operated by Belgians who didn’t know the language and made numerous spelling errors (such as “busy” in place of “bisy”). And because they were paid by the line, they sometimes padded words with extra letters; “frend,” for example, became “friend.” In the next century, other non-English speakers in continental Europe printed the first English Bibles, introducing yet more errors. Worse, those Bibles were then copied, and the writing became increasingly corrupted with each subsequent rendition. English spelling became a chaotic mess, and successful attempts to simplify the spelling after that were offset by events that made the language harder to learn, such as the inclusion of many alternate spellings in Samuel Johnson’s influential English dictionary. Unlike many other languages, English spelling was never reformed to eliminate the incongruities. In a sense, English speakers now talk in one language but write a different one.
As a result, there’s no systematic way to learn to read or write modern English—people have to memorize the spelling of thousands of individual words, file them away in their mental databases, and retrieve them when needed. A small percentage of people excel at this skill, but for most children in English-speaking countries, learning to read and write their native language is a laborious and time-consuming exercise.