Presumably €10,000 is the trade-off value which the member states decided would be sufficient to make an impact on money laundering without imposing too much bureaucracy on small transactions.

> Why should the people follow these insane rules?

I don't necessary like them, but AML 4/5/6 are well-reasoned Directives that were written and negotiated in public and agreed on by all member states. They didn't receive much pushback during their drafting periods. If anything, leaks like the Panama Papers have made them popular.

As for why people should follow the law, that should be obvious. The state won't leave you alone to transact as you wish. Compliance failures lead to civil and criminal sanctions.

> In the us this is potentially unconstitutional unless it is interstate trade.

Fortunately, the EU is not in the US.