You have to remember that Crappie Nibbles are used to attract the fish however I believe they are more effective in getting the fish to hold on to the jig a second or two longer because of the taste. Fish inhale or taste the bait usually and having the nibble will get the fish to hold it or hit it again to get the taste and give you time to set the hook. This is the reason most use the nibbles with jigs.
Minnows are a whole different bait. They are lively and move on their own and have scent built in and taste as they taste to fish. No need to use a third party attractant.
Also the nibbles are best "molded" onto the hook at the very tip to entice the bite there.