I wonder what benefit to society might having a shadow financial system bring? I can't think of any, except for financing entities operating outside lawful limits.
The idea is that "lawful limits", even if you wholeheartedly support them now, can change at a whim if a new government is elected or a war starts or some other major crisis happens. These things come and go every few decades, one is not improbable to occur within the frame of your lifetime and place of residence.
Never did much care for Rousseau myself though, or the fascists and communists he spawned.
For example the fact that ruzzia ha such a stable budget for 3 years in row is not in a last part due to the token system, where they can trade with Iran, China, and others and launder tokens through UAE/SA/Qatar exchanges etc.