It's also not uncommon for telecom providers to use it for their own internal routing because enough telecom software did in fact develop support for it despite lack of public implementations.

As someone who's been in the VoIP industry for over 20 years it makes me sad to think of what could have been if both ENUM and IPv6 were more widely adopted. For many years you could reach me via email, SIP, or Jabber with the same identifier and if there were effective support for ENUM in the USA my work phone number would have been able to connect you to any of them, directly and with G.722 HD voice long before it eventually came to modern cellular networks.