I can’t know for absolute certain, but the data seems to suggest that supers and carriers are the problem: CCP tried to take care of it a year ago (they just went about it in the wrong way IMO), but ultimately scaled back their efforts due to player feedback. [June] Fighter Damage Reduction - Upcoming Feature and Change Feedback Center - EVE Online Forums
As of May 2017, 46.2% of all bounties were made by a mere 6.2% of players using carriers or super-carriers. Comparing economic reports from that time to now, not a lot has changed in terms of total bounties, and bounties are concentrated in the region with the largest super fleet in the game, strongly suggesting that the issue is still super and carrier ratting.
It’s not an issue directly; it’s an issue because a high degree of safety while super and carrier ratting encourages people to rat in supers and carriers resulting in a massive amount of isk brought into the game via bounties. HAW dreads arguably could be pretty good at running sites, but the practice is nearly unheard of outside of wormholes due to the risk associated with sieging in nullsec.