Wedding reception Catering by Indimax Caterers

Can someone explain this wedding joke to me? Apparently a nasty woman was roasted. See, at my brother's wedding reception, I went into the hall to use the bathroom, and I saw the manager scolding this caterer. Apparently he signed up for some one-person coffee service. She told him she didn't think he could manage it alone (tactless and belittling by the way) and was all, "I told you not to sign up for shifts by yourself. You need someone to guide you. I don't know how much clearer I can be for you to listen" (something like that, so don't quote me on how I quote her). The caterer (who I'm guessing has learning difficulties) resentfully said in a sassy tone, "You know, I'm beginning to see why you put weddings and receptions in your profession."