This is the norm in more industries than you would expect. A primary example is food service. You have a main job function, but you do whatever is required of you. Dishwasher busted in the middle of the shift? Grab a bus boy and have him help out washing by hand. Late night surge because some concert let out that you didn't know about or plan for and they all decided your food sounded good? Well sometimes the manager rolls up their sleeves and hops behind the line to help cook. Not enough hostesses? Waiters are stepping in to help greet and seat customers.