In this case, perhaps there are a couple of factors. First, for many Americans, it's very against their sense of fairness to apply unwritten rules, especially

In this case, perhaps there are a couple of factors. First, for many Americans, it's very against their sense of fairness to apply unwritten rules, especially after the fact. I'm not sure about other places, but the U.S. has a long history of unwritten conventions being applied unevenly to the detriment of less powerful groups within society. The U.S. also has had to deal a fair amount with multiple cultures living near each other in a single society, and the convention has become that unless cultural expectations become codified in the laws by which we have all (by proxy) agreed to live by, it's very rude to try to force your cultural norms on someone's behavior without at least campaigning to get those norms codified in law so they are uniformly applied. To many Americans, there's the sneaking suspicion that standards are being unequally applied if someone is being to be asked to go beyond what the law requires if there isn't simultaneously a strong push to codify these unwritten expectations in law. The second factor is perhaps the American cultural bias towards individualism, distrust of government, "go big or go home", and a tendency to view theory as only a means to an end (application). "Why theorize about what should be done if your aim is not to change the laws that govern all of us?" Most Americans don't view governments as worthy recipients (or good stewards) of voluntary donations, and view any non-mandatory taxes paid as donations.