Have you wondered why words such as knight and lamb have letters in them that are not pronounced? To understand English spelling, it helps to know that once those letters were pronounced. However, after the invention of the printing press around 1440, printers started to standardise spelling over the next couple of centuries. When the pronunciation of some words changed, the spelling had already been 'set in print'.
So why not change the spelling now? Some people argue that we should spell words phonetically (i.e. the way they sound). There are significant reasons why this would NOT be a good idea. Can you think of any?
One really practical problem with that is that there are so many different accents that different parts of the world would spell the same word differently so we would end up with total confusion.
There is also another important reason. The spelling of lots of words provides clues to their meaning. English is full of word families, that is, words that have been built around the same root word - and these have been borrowed mainly from Greek, Latin and French. The word phonetically is a good example. It is based on the Greek phon(e), which means 'voice, sound'. If we were to spell the word phonetically the way that it sounds (i.e., phonetically), we would lose that information, that clue. We would not see its relationship with other words such as megaphone (big sound), microphone (small sound) and a host of other words in the same family - all based on phon(e). If we recognise word families, it helps us work out and remember the meanings of words...and the spelling makes sense.
Apart from those reasons, it is also helpful to be able to distinguish between words that sound the same but have different meanings. Imagine if we could not distinguish between flower and flour or night and knight or isle and aisle!