Designers are expected to also be able to package and ship goods, work the cash register, and do other retail based tasks that they may not be trained for beyond what they learn in store. While they do help you if you're inexperienced with how to handle things when they go badly if a customer gives the store a bad review because of your poor service you will get in trouble. This is not just limited to bad behavior like rudeness or language but can also include situations like getting flustered because the computer system crashes or if the shipping program takes several attempts to print a label for a package (which happens a lot).