You've just brought another angle to this argument. I don't know how popular the word "jiffy" is nowadays, but it was common throughout most of my life. "In a jiffy" means something will be done quickly, and the word is sometimes shortened to "jiff" (ie. "It'll only take a jiff.").You know, I would've understood the point of this if "jiff" meant something fundamentally different from "giff", but it doesn't. Usually, when you say either of those, people know what you're talking about.
Mostly because people don't stop arguing about it.
So between doing something quickly (jiffy/jiff) and peanut butter (Jif), it's a lot less confusing if .gif is pronounced "gif" with a hard "g".