At least one of your items, telephone numbers have their own URI scheme [0] (in the original model, URNs were non-locators while URLs were locators; telephone numbers are arguably locators, but in any case URLs being replaced with URIs, which need not be locators, and URNs becoming a URI scheme mean that there is really very little good rule as to when a non-locator identifier should be a URN namespace vs. its own scheme.)

Also, the same rationale that led to the closure of the registry foe the somewhat similar info: scheme registry [1] likely contribute to limited registration for URN NIDs.

[0] tel: (RFC 3966) https://www.ietf.org/rfc/rfc3966.txt

[1] https://oclc-research.github.io/infoURI-Frozen/