

“Legally required”, so they’re seeing it in the local laws. Some countries require websites to disclose who operates them.
For example, in Germany, websites are subject to the DDG (Digitale-Dienste-Gesetz, “digital services law”). Under this law they are subject to the same disclosure requirements as print media. At a minimum, this includes the full name, address, and email address. Websites updated operated by companies or for certain purposes can need much more stuff in there.
Your website must have a complete imprint that can easily and obviously be reached from any part of the website and is explicitly called “imprint”.
These rules are meaningless to someone hosting a website in Kenya, Australia, or Canada. But if you run a website in Germany you’d better familiarize yourself with them.
Those are typically early joiners who got special conditions. The idea is for everyone to adopt the Euro at some point. (The UK wouldn’t have but that’s moot since they left. If they rejoin they most likely won’t get that special treatment anymore.)