When the payoff of cultivation might take years or even decades, or worse yet never and you die trying to reach the next step. Becoming the most hated sect around doesn't seem like such a bad ending...
TBH, I dont understand why demonic sects are hated on in most novels. This I understand, due to them absorbing others, but in other novels, where they don't, I don't understand it at all. Like the whole unorthodox/orthodox thing.