Gold and banknotes also have the property of being bearer assets but they're less worrying if you're the authorities because they're physical.

You can (and people often do especially with banknotes) do crime and tax evasion with them, but you can't transport them across borders in large quantities easily.

Something like monero has the potential to be almost as fast and convenient as a fiat bank transfer but able to be done in any size and be untraceable - that's a combination that doesn't win you many friends in western governments