Nor is it due to the existence of shell companies. Rather it's due to poor enforcement and loopholes in tax law. You also don't need to make any of the information public to enforce it anymore than it's required to make your personal earning information public to enforce you paying taxes.

It's hard to take that position seriously. The people using the loopholes are the ones that pushed to put them in the law and degraded enforcement budgets. One hand washes the other and it takes place in the dark. Let's put a little sunshine on it and see what happens. We might find some very interesting networks exist...