What valid purpose does hidden numbers have? Government departments in my country hide their caller ID.
I find that abusive on its own but let’s not forget about the fact that now you have victims of domestic violence being forced to answer hidden numbers in case it’s welfare, or the cops, or their abusive spouse.
Calling in an anonymous tip to the police and such.
I’d say to use a payphone if you need to do that, but then my age is showing, as this is not possible anymore.