With some vendor such as Eva Levante, you can always go back and regain items previously purchased or earned. But items like ghosts, artifacts, and marks do not have this option. Why not give The Traveler a similar kiosk\data board where all previously earned and purchased ghosts, artifacts, and marks\cloaks\bands can be accessed and regained? It's not like The Traveler really has a role anymore anyway so at least by giving us this option, we have a reason to go to him again.