The Stupid Reason:
It all comes down to sloppy handwriting. In medieval times, highly stylized writing focused on the "minims," or vertical lines in a letter, and the smudgy nature of ink confused people trying to read it. For example, "in," "ni," "m," "iii," "ui," and "iu" might all look exactly the same because the horizontal lines written into each letter were so thin, they tended to smudge or just fade away. For example, this:
This says "animal," like you fancy yourself in the sack, or "annnal," which is a rather annoying way to ask for it, or "aiiuiiai," which is the sound you're going to make when you head for your partner's fire door without permission and get punched in the throat. The solution to all this buggery was to just stop using "u" for some words, like "some," "love," and "come," and wow, we just cannot get out of the gutter here. This is the reason why you see an "o" for a "u" sound when it's next to an "n" or an "m," like in "monkey" and "ton," and also why you see a "c" before a "k" when the letter appears next to more minims. The "c" was a good way to separate the "k" from letters it could be easily confused with, which led to spellings such as "lick" and "flick" and ... we're going to open a new tab here and take care of some things before this next entry.
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By which we mean listening to some classic Slick Rick.