Isn't this more of a cultural thing, that Germans seem to agree that it is authoritative and use it as a reference? I'm not sure what would even make a diction

Isn't this more of a cultural thing, that Germans seem to agree that it is authoritative and use it as a reference? I'm not sure what would even make a dictionary prescriptive other than an explicit declaration that it is so or, ridiculously, a law declaring the same.