Here's why:
* Short vowel sounds are typically found in words with one syllable and where the vowel sound is short and quick.
* "Kiwi" has two syllables ("kee-wee").
* The "i" in "kiwi" makes a long vowel sound. It sounds like the "ee" in "see".
So, while "kiwi" is a short word, it doesn't have a short vowel sound.