One of the issues here may be that neos[porin/triple antibiotic seems less favored in ER usage and therefore less studied than is  
bacitracin   anecdotally related to a better allergy profile.   
Probably a few reasons: 
-1 drug versus 3, so less chance for allergic reaction
-works fairly well (you'll notice bacitracin is the main drug in neosporin too)
-CHEAPER, probably