because the drummers will be sued for "DISTRUPTION" or something. Besides the North American System is far efficient. We have in Canada for example Federal(GST) and Provincial Tax Auditors who goes around checking questionable bookeeping records. However, people still has a way of going around not paying their taxes if their smarty (cunning) enough.
...grey market, is just one of the example.
In South East Asia, Asia and other parts of the world, it is more difficult to track outgoing expenditures and incoming revenues because people are so used to paying cash for almost everything. Many do not deposit their money --- stashed away in some part of their houses or some Swish Bank Account...blah blah. However, slowly, the system is changing.