Don't forget that Bungie made daily Queen's bounties so you can chase that armor set. Bungie promoted Days of Iron sets, Wrath of Machine sets, Archon's Forge sets, chroma sets, ornament sets... as well as bringing all year 2 armor forward. For all the people that see a vault space post and come in to blast people as hoarders: collecting sets are part of the Destiny experience. They have always been part of the experience but really started becoming heavily advertised in Rise of Iron and The Dawning as an activity. Bungie uses armor sets in its marketing. So naturally we go out and chase them. Even more naturally, we want to keep them. Again, Bungie, especially in ROI and The Dawning, advertised armor sets to entice players to spend money on the game. Instead of giving us more vault space, they put development resources into another kiosk that facilitates more microtransactions through ornaments and silver dust as well as a holiday kiosk for the same reason.