Being an avid smallmouth bass angler as well as a crappie/gill fisherman, I can tell you that they can "help" at times. By help, I mean they can enhance your
confidence level. That's about all anything can do at the end of your line, right? You choose jigs, plastics, cranks, etc., based on what you
believe will increase your success. So if you feel that scent gives you a slight edge, why not go for it? Myself, at times I apply some
MegaSrike attractant. Sometimes I don't. Depends on my mindset at the moment.
Just remember, depth & speed control are the absolute defining factors to success. Everything else after that is pure speculative, in my opinion.