Packaging design is about shelf presence and gentle persuasion - okay perhaps not so gentle! People must see it and then be persuaded to buy it.
Great packaging won't sell a product more than once if the product is no good. Bad packaging will stop a product being sold no matter how good it is. Good packaging design will attract, appeal and persuade the consumer to buy.
If you've got your product right then why skimp on its presentation. Make sure your target consumer is attracted to it and keeps coming back for more.