Many mysteries in Destiny revolve around Xur, the Agent of the Nine. He is a merchant who only appears in the Tower at specific times and brings exotic items.
At the beginning of Destiny, this was such an unusual gameplay mechanic that it took a long time for the Guardians to fully understand it. The “strange coins” that Xur accepted as currency were rare for a long time.
Especially mean: In the second week after the launch, Xur brought the rocket launcher “Gjallarhorn”. The best and also rarest weapon in all of Destiny for a long, long time.

But back then, there was barely a community, hardly any fan sites or YouTubers covering Destiny, who already had any clue about the game. The gaming press also had to find its way in the game.
Those who already had so many strange coins that they could buy the Gjallarhorn often decided against it: Giving up an exotic slot for a rocket launcher? No way. Not a chance.
And thus, the greatest gift that Xur ever wanted to give to the Guardians remained neglected, and he was not thanked for it. Can anyone blame him for being such a greedy son of an octopus since then?