Remember back when there was the preview bug in the ornaments loadout page and bungie said "oops yes we'll fix that we know"? It was cool seeing what they'd look like on armor.. they intentionally did it to dangle the carrot in front of us, mementos are glorified shaders that are restricted to only crafted/enhanced weapons and put behind a rank 30 lockout We have like 5-6 mementos and they couldn't be bothered to just extract the shaders and put them in the game or make them only show up on tier 5s (all of them, incl. raid ones, as long as you've earned one at any given time at least once)