35 years ago the IETF defined special IPv4 addresses in RFC 1597 to be used solely in private intranets and with that created the separation between internal networks and the internet. 5 years later they proceeded to define special-use top-level domains like
.test in RFC 2606. However, the IETF did not reserve a top-level domain to be used within the private intranets that they had introduced before. This lead to confusion with administrators that still persists to the current day.