@kalledank
I think they did it so that non-legends would feel compelled to help legends with the legendary voyages. If both a Legend and non-legend cannot mutually benefit from a certain task, then there is disagreement, and then legends and non-legends become more inclined not to play together.
I do not think that justifies allowing non-legends to purchase legendary cosmetics, they should only get the Athena Rep for it.
And before anyone disagrees that they are not legend cosmetics, they are Pirate Legend cosmetics, despite what anyone tells you - they are purchased in the Pirate Legend Shop, in the Pirate Legend hideout which can only be opened by a Pirate Legend, and can only be obtained through doing voyages that only Pirate Legends can access and initiate.
They are Pirate Legend cosmetics 100% and it sucks that Rare let non-legends get them. Rare just need to be sure that anything new from the Ghost set, such as equipment, weapons, and extended ship cosmetics remain locked to being a Pirate Legend. At least that way, someone who obtains the full ghost outfit and has the matching weapons and equipment can really be represented as a legend.