That one registrar is chartered and controlled by a government; for much of the Internet, that government is the United States, which already has a system in place for seizing control of domain names. I'm baffled that people could be sanguine about also giving them control of encryption certificates.

DNSCurve doesn't authenticate DNS data. It authenticates the connection between the client and the server. It does that because authenticating the data requires boiling the ocean by getting a huge portion of the Internet to agree on and implement a scheme to authenticate data, and authenticating individual connections works even if you and your server are the only people who agree to do it. DNSCurve solves a less ambitious problem than DNSSEC does, but that problem is (a) the most important problem in DNS security and (b) actually solvable, unlike the DNSSEC problem.