I agree with Phavoc’s comments on the prior thread: the wiki comments regarding banking when information speed is largely limited to travel speed is bunk. Such problems can and historically have been overcome. A ship or individual outrunning their banking information is a real issue, but not an insurmountable one.
Keep in mind that classic traveller was written in 1977, long before cryptocurrency. In the 70s the US Navy paid sailors at sea in cash. No reason to do so now, and even then electronic commerce existed, just not at today’s scale.
The wiki also states encryption is essentially impossible due to quantum computing. If that’s true, you essentially have a society with zero privacy, which has implications far beyond the financial sector. No personal, corporate, or government record stored electronically can be secure in that scenario.
No government is going to allow a cash only society to exist more than they have to. Electronic records have a very useful purpose: proof of taxes owed. That’s a major issue with the marijuana business in the US. Selling dope is legalized under many states, but federally chartered banks ( pp(and many small banks) won’t accept their deposits, because that’s money laundering under federal law. So everything is done in cash, or at least it was a few years ago. This makes fraud very easy, and the industry much more difficult to regulate.