There's reasons for bad perks to exist, and they're almost necessary. 1 If only good perks were around, then everyone would get great rolls on weapons much quicker (Which was a problem in year 1, although it was a bit different), 2 people like finding hidden gems, sometimes perks that seem bad can have unique or fun applications. and 3 what perks are bad is subjective, and if bungie decided "bad" perks needed to go, lots of players who enjoyed them would lose out, also even if a perk is "bad" or not very effective in the traditional sense it can still be fun to use, and in the end having fun guns to use is bungie's goal. I assume you're at least partially referring to the ritual weapons like bottom dollar or the keening, they're designed to be that way so each time you get a roll, it's worth looking at and thinking about, as well as because they're tied to activities that are played so often, they need to have that variety or else you'd get a god roll too fast, and then it provides less incentive to play those activities that are designed to be repeatable endlessly with minimal staleness.

Any chance you could give more examples of the perks(their names or what they are)?