This shows how little cryptocurrency users know about how governments collect taxes. The government doesn't go around checking people's bank accounts in order to get tax information. This would be terribly inefficient. What they do instead is pass laws that require employers to disclose how much they pay their employees and to collect taxes on their behalf, before the taxpayer even receives the money. Therefore private transactions and 'unconfiscatable' money does nothing to prevent governments from collecting taxes, at least as far as ordinary people are concerned.