User blog comment:ImperiexSeed/The oldest being, archangel or leviathan?/@comment-5110811-20120811220745/@comment-1509826-20120913202004

Two reasons, one for atleast one horseman, he never showed his full potential, I mean War was just starting out, what happened in the town, was mearly the warm up, he was planning to spread Chaos around the entire of america, if not the world, so he never used his abilities to there full potential.

And Two, its implied they were once stronger, but due to improvements in Hygine, Farming Techniquies and Peaceful negotiation, the number of incurable illnesses, famines and Wars have decreased, as there the actual embodiments of these forces, rather than simple representations, weaking them, has caused the horsemen to be weakened. As people still die, and at a great rate, Death does no have this problem.