As this site explains, the Latin language nearly abandoned the Greek "kappa," preferring "C," which ultimately led to redundancies when Greek and other foreign words that involved a hard "k" sound were adopted and then absorbed into English.
The Romance alphabets include the letter "k" only for loan words. In Italian, the "k" sound is otherwise represented by the combination "ch." For example, the word "chiaro" ("clear") is pronounced with an initial "k" sound -- "kee-AH-ro."
Another good reason why English spelling drives people crazy.