It's not rare in the aspect of how it's obtained but more so in that it requires exogenous protocols outside of 'just playing the game' to aquire. One must initially suffer the perils of spam mail, if they're lucky to ever get the email to their inbox in the first place and not automatically gone straight to spam.... After all that mess, 95% don't wear it or even know that they have it. I get 10-15 'Exotics' in the game a day....so if Bungie can call that an Exotic it's fair game for me to call an item worn by less the say .05% of the population as rare :)