It's a good thing that nobody has ever been massively fucked over by a regulated fiat system.
"God look at all the people killed by that airplane attack... let's get rid of skyscrapers and/or airplanes!"
"Man, alcohol sure does fuck over a lot of families, let's prohibit it!"
"That computer-based system led to millions of dollars being lost, we should stop using computers!"
Face it, now the same argument that you would use in support of still using Bitcoin exchanges (presumably run by more competent individuals?) would also work in support of regulated fiat systems (especially those run by more competent individuals!).
Unregulated currency by cryptography is novel, but doesn't create an inherently new concept any more than digital cryptography did not innovate encipherment or authenticity checking.