DNS can contain all sorts of records that, at some point, someone thought was worth standardising. In this case, I assume it used to be so common for a sub-dom

DNS can contain all sorts of records that, at some point, someone thought was worth standardising. In this case, I assume it used to be so common for a sub-domain to refer to a single physical box that there was utility in knowing exactly where in the world it was. Cf https://www.ibiblio.org/harris/500milemail.html https://www.ibiblio.org/harris/500milemail.html