Because Bungie looks at weapon diversity on the community level instead of on the individual level. Bungie would rather the individual only use the same 3 weapons for 2+ years if it means each individual uses one single variant. Short sighted and a tale tell sign that they have biased approach to reading analytics. Year 1 a player could evaluate what weapons to bring to an activity based on jobs needing to perform. This made players efficient. Y2 a player now just brute forces their way with the same weapon they've used for 15 months. This also provides artificial difficulty. Using a hammer to drive in a nail is efficient. Using a screw driver to hammer in a nail makes the task more difficult without changing the task. Using a screw driver as a hammer with the excuse "everyone's using hammers" is a distraction from the real goal. Nerf the guardian because that's easier than improving the activity.