Some weapons have no excuse. They have been out long enough. But newer ones get theirs after bungie looks at how good the original is in the game. For example, Lumina was a great idea and is one of a kind. But it hardly got any usage despite being decent. The catalyst is very very strong in basically any activity where you aren’t stupidly under leveled. So a strong catalyst on a weapon will elevate its usage beyond what it was already without having to change perks or its weapon archetype. I still don’t know why izanagis burden got the catalyst it did though 🤷🏻‍♂️ but others than that, that’s what happens.