Government now implementing law to avoid this scenario. Though it's not followed by the others because they want "decentralized system" to avoid or bypass taxation. The Anti Money Laundering law(AML) is implemented to avoid people from bypassing their burden tax through Know Your Customer(KYC) which force to reveal the identity of the crypto user before they withdraw and liquidate their cyptos. Every bank uses KYC to know who uses their service and what kind of transactions he/she made. Many people don't like it but there's nothing much they can do about it. Yes, people use dark web to buy stuffs there. But to liquidate crypto, it is impossible to do without being traced or reveal your identity.