There are no "calls" for them to pay their fair share because for the most part they already are, in many cases well more than they can afford. Your comment also implicitly presumes that the wealthy were already paying their fair share, and this is some extra burden arbitrarily heaped upon them by an unkind majority.
How much, exactly, is "society's" fair share of someone else's money?
This is the problem. There is this assumption that taxes are used to care for the destitute. Absolutely, some amount of taxes do go to that end.
However, I've worked enough government contracts to know that the vast majority of that money goes to providing middle-class incomes for people in government who otherwise would not be making that sort of money because of a distinct lack of intelligence, competence, or diligence.