Gear that can be purchased and repurchased typically doesn't make it into the Armoire. Its purpose is to hold items that can never be acquired again, like the original quested AF, or gear from old holiday events. Note, many of these items CAN be acquired again, now, via the cash shop or the Calamity Salvager, but at the time they were added to the Armoire if you threw them way they were Gone Forever. The purpose of the Armoire is to prevent folks from being frustrated by the fact that they have to choose between using precious inventory space and throwing away something that's outdated but irreplacable.

AF2, if you throw it away, you can always build up tomestones to buy a replacement. It may not be fun to do, but you have that ability. Even when Tomestones move on to bigger and better armor, AF2 will still be available in some form, much like the dungeon-dropped tokens that allow you to acquire Relic armor.