Of course cosmetic packaging designers aren't in great supply. But those who have worked within the industry often do so with huge success. They have the knowledge and experience to know exactly what consumers are looking for and will also ensure that any brand identifiers are carried through.
The divide between success and failure in any commercial industry is often very fine. Nowhere is this more true than cosmetics though. Consumers know what they're looking for and have specific expectations from the products and their Cosmetic Packaging.
If you are able to create cosmetic packaging that leaves your competitors in the shade, your chances of attracting undecided shoppers are greatly improved. Stand out and be successful or blend into the background and face the consequences. It might not seem like the biggest priority, but consumers are a fickle bunch and you have to make sure you're speaking their language.