Here's why:
* The vowel sound in "pants" is a long "a" sound, as in "say" or "day". It's spelled with an "a" followed by an "n", which usually indicates a long vowel sound.
* Short vowel sounds are typically represented by a single vowel letter (like "a" in "cat" or "i" in "pig").
So, "pants" does not have a short vowel sound.