Cloudflare is the latest in a number of different CDN providers we've used to serve this over many years. I guess the question is, why is it important not to use a CDN?

Same reason everyone else uses CF. Static page CDN only became too cheap to meter ~16 years ago, but if CF was around in the 90s IANA would have used it in the 90s too

IANA has a history of hosting even more important services with third-parties [0] [1], so this doesn't seem too problematic to me.

[0]: https://root-servers.org/

[1]: https://datatracker.ietf.org/doc/html/rfc6305.html

NB. IANA isn't responsible for "root servers"

It's only responsible for root.zone, root.hints, .arpa and .int zones

AS112 is a volunteer project not a company

If it's a name in com/net/org only meant for documentation then why serve a page there for decades. If traffic is a problem then take it offline

Years ago IANA started requiring a user-agent header

FTP access to root.zone remains

*assets

Well, it's a popular website. By using Cloudflare I think they will save a lot of bandwidth and traffic because the page and assets can be cached.