It works because that's not the calculation being made. You're not giving up money specifically to a "Steve" or "Joe". What you are doing is putting money into a pool. From that pool, the money is redistributed in such a way as to provide baseline income to people in need. Most of the people it is redistributed to are not "Steve" or "Joe", and the calculation is that it is cheaper to ignore free riders such as Steve/Joe as they are a small minority. The calculation is also that not providing this baseline is both economically bad (providing a baseline seems to be much more cost effective than dealing with effects of not doing that) and morally bad (most of the people in need of the baseline are in need of it not [directly] through fault of their own)