Nah, it's because it tends to be an exclusive item from another region or something that was once an event exclusive and is no longer obtainable. So while you the player might of paid the 12.99 that month to play the game and get the item when the event was available, now a player who rejoins and wanted that item can instead pay with money to get that item because the sub fee in a sense acts as the key to get those items for "free" because they are designed to be perks for staying loyal and playing/subscribing.
As for the Chinese and Korean outfits, these were specially designed and also special promotions I believe, so to make them "free" to our servers would be very bad PR on SE's part because then it be like saying "Ok we'll have the Koreans and Chinese pay to get those outfits but the NA/EU/JP can get it for free!" and they don't want to suggest that they are giving it away to free to another version when the original version had to pay for it in some way.
