Here's why:
* You can have more than one: You can have two kites, three kites, a dozen kites, etc.
* You can use numbers with it: "I saw three kites flying in the sky."
* You can make it plural: The plural of "kite" is "kites".
Uncountable nouns, on the other hand, cannot be counted individually (like "water" or "information"). You can't have "two waters" or "three informations".