Why doesn't nasa.gov have a root A record?
I attempted to visit http://nasa.gov/, but got "Server not found", so I checked https://dnsquery.org/dnsquery/nasa.gov/A and there is no A record. Does anyone know why not?
There is an A-record for www -- the canonical reason I heard "back when it was common" for leaving the origin record blank was that your domain might have several different hosts providing different services across different protocols, and you don't want to lead anyone to believe that they can "just go to nasa.gov" and access the FTP archives there.
Dumbing it down a bit but that's the idea.
In actual practice, it seems very uncommon today to leave the origin record blank like this, and I think it's probably an oversight, or a side effect of an organization being around since the internet began in a bureaucracy as large as the US government. It would probably take an act of congress to get this updated, only half-joking.
Unfortunately domains and DNS servers that allow public AXFR for easy discovery of answers to questions like this (what other subdomains does nasa.gov respond to?) are just about as few and far between.
Not least of which on the list of reasons, because I believe AXFR can be used in redirection/amplification style DDOS attacks, so it's probably considered a vulnerability to respond to AXFR from arbitrary requestors.