It’s not the fact they have to do duties outside their core-responsibilities, it’s the fact that they aren’t being paid a suitable wage when they have to do those duties and forego tips.
Sorry that I can’t agree.
Those duties were part of the job.
Even today, when I have left the service industry, there are things that I am required to do that are outside of my job description. My employer doesn’t drop my wages to coincide with those tasks.