It could be that I'm wrong in my reasoning, but it appears to me that bitcoin allows tax evasion and black markets to function on such a breathtaking scale.

Bitcoin has less anonymity than cash. Every movement of coins is recorded in a publicly verified ledger. You can use some trickery like CoinJoins to try to regain some privacy, but even these can be mitigated by state-level actors, and don't solve the problem that actually spending coins typically revels your real-world identity to the merchant you are interacting with (who must comply with local KYC laws).

You know what allows tax evasion and black markets on a breathtaking scale? Greenbacks. Do you think a criminal - even a technically competent one - would prefer a suitcase of cash or bitcoin transaction? One of these is, outside of extenuous circumstances, truly anonymous and untraceable.