The assumption that bitcoin is anonymous isn't really a great one. It's pseudonymous at the very least, but as it's possible to track every transaction ever mad

The assumption that bitcoin is anonymous isn't really a great one. It's pseudonymous at the very least, but as it's possible to track every transaction ever made (even moreso than cash transactions), it's not a trivial matter for typical users to anonymize their transactions. Even if Bitcoin (and tumblers) became ubiquitous, the legal frameworks that exist to handle cash transactions (e.g. making an unusually large amount of cash purchases of gift cards, moving an unusually large amount of money across the border, etc.) will be revised to include bitcoin, with the result that using BTC in the way that people seem to think it's destined for will become, if not illegal, then at the very least highly suspect. Ideally, we should be fixing the broken systems that are in place, rather than trying to concoct technology to try to work around it (which can then just be regulated/criminalized anyway).