It's a long story, but I put it in my recipe as a "Secret Ingredient" because one of my buddies is a bit of a purist (okay, the dude's a snob) when it comes to Cajun cooking and spices. Which is really weird, because he's from Iowa and has never spent more than a week in Louisiana in his whole life. Anyway, last year he went off on this whole tirade about how Old Bay seasoning isn't "authentic Creole" and how "nobody south of Tennessee ever uses it."
Now I grew up 2 hours from Shreveport, and I have family in Monroe, but what do I know?