I'll gladly explain.
The state may have the power to go after the bad actors, but Bitcoin makes it far more difficult, because pseudonymity. Unlike fiat, Bitcoin transactions are not linked to identities - only addys.
The state also has no real interest in maintaining a semblance of order & respectability in a pseudocurrency meant to unseat the state-backed money. It has great interest in maintaining the value of the currency it issues, but Bitcoin's value? Not so much

TL;DR: No mechanism for self-governance; no incentive for state to help; more difficult to enforce even if the incentive was there.
@Lardass: ur fat.
Law enforcement testified at the NYDFS hearings last year and they repeatedly said bitcoin did not make their job any harder in regards to catching criminals.
Fiat is not linked to identities. Credit cards might be, bank transfers might be, but fiat itself is not linked to identities.