The brand is a continuous series of interactions that the consumer/user invests into. We sell this interactions as a series of communicated weaved with a common story and it only in your personal interest to make sure that your story ties into your packaging experience.
If you are seeking evidence, then look at the youtube influencers who review unboxing experience that are watched by billions of users before they make purchases. Your brand experience effectively is not completely now owned by the brand.
Over the years, as eCommerce and online retail has also plunged in. Its made it rather difficult to own your brand experience but packaging is still something that remain in your organizations custody. Its a handover point, where you deliver your promise.
Packaging is obviously not as easy as digital design, once you start off, one must consider a lot of options around the same. From rigid packaging to corrugated one, time to deliver, packaging prints and design and optimizing costs accordingly. While all these questions get answered, when you are consulting with a packaging firm but bring yourself a little upto speed on what different kinds usually are in the works helps in making more informed decisions.