Going to be tough for my two sisters to take any leftovers home with them. One lives 800 miles away the the other 2500 miles away. Looking forward to their visit as I haven't seen one of them in 35 years.
As for the topic, I don't go expecting leftovers. If the host insists that I take some then I gladly will. In the southern tradition, if they give it to me in one of their dishes, I return the dish with a a nice homemade treat of some sort for them to enjoy later. In the modern day they usually put it in a disposable plastic container though and so that method of giving thanks has mostly disappeared.