[dns-operations] Dumb question: why is it that some registries limit the nameservers that can be delegated to?

[Colm MacCárthaigh]

Many registries, if not most, don't let you delegate a zone to
arbitrary name-servers. Instead those nameservers need to be
"registered" in some way.

Typically anyone can register a name server, and it once it's done,
many zones can be delegated to that name server. A small number of
CC-TLDs also require contact details for the name servers, but I only
know of two that do that.

Registering doesn't require setting up glue, and it doesn't look it's
being done to detect cyclic dependencies between zones, which is also
the only limitation in the DNS that I can think of that require some
kind of workaround.

So why is it that name servers need to be registered? What's the
benefit of doing it? and if anyone can register a name server, what's
the point?

-- 
Colm