The way this worked was there's a very large amount of keys accepted by the installer and a very tiny fraction of them are actually issued / valid for online play.

There wasn't that much value in having the installer keys be that narrow; if you have a legal cd it'll have the key printed right on the case (and there's no way to stop sharing). If it's a burned cd either the person who ripped it can just include the key or they can edit the installer itself to accept any key.