Lineage II never had cloaks. It's funny that we never really realized this before, but those characters just never wore cloaks. Luckily, the developers have realized their oversight and have finally fixed it -- cloaks will now be available to characters in the Gracia Final expansion. However, don't expect that you'll get a cloak just for logging in.
Cloaks are reserved for players who fight in Territory War, have high ranks in their clan, and those who fight against some of the major raid bosses of the game. The cloak rewards for these accomplishments are the Ancient Cloak, Knight's Cloak, and Holy Spirit cloak respectively.