Anise Oil has been used, successfully, for decades to attract fish to lures. Some have even gone to putting the oil in their bags of plastic baits (while stored, prior to use).

I can't say it works or doesn't work for Crappie, as I've mostly used that particular scent on plastics I used to fish for Bass (decades ago). But, I would tend to think that Anise Oil would be just as effective as many other scent products in masking any negative scents that might come in contact with your bait ... like tobacco, gas/oil, bug spray, sunscreens, & human amino acids (from some people).

So whether it's actually an attractant or merely a masking agent, it's still being used by many anglers.