Here's why:
* The "a" in "have" has a long "a" sound. It sounds like the "a" in "say" or "day".
* Short "a" sounds are typically found in words like "cat", "hat", "man", and "ran". They are often spelled with the letter "a" followed by a consonant.
So, while "have" does contain the letter "a", it is not pronounced with a short "a" sound.