I think you are spot on. Cryptocurrencies that fully obfuscate amounts sent, sources, and destinations, are perfectly ideal to hide assets. I think most people, even the tech crowd on HN, are unaware of their advanced capabilities.
If some of the most sophisticated operators were caught (vis-a-vis DPR (Silkroad)), why would "regular" families of wealth take a chance with crypto? I would humbly submit that regular tax evasion via LLC's, trusts and other holdings are much easier.