Me too (for IMAP and other things). Maybe IANA is a starting point for
"advanced" users, but I think it does serve a very useful purpose for
developers.
And same here for DNS types.
Yes, indeed. There's no other reasonable way to figure out what some
random rrtype is supposed to do. (Grepping the RFC collection, while
possible, is not reasonable.)
I'd say I look at IANA protocol registries a couple of times a month
both for DNS and other stuff. No doubt there are programmers and
designers who never look at the registries, but there are also plenty
of them who never look at RFCs either. Let's not go down that rat
hole.
R's,
John