It is the content that should be evaluated not payout.
As I understand it, the content is evaluated in terms of whether or not the subjectively perceived value of a post is in agreement with it´s reward level at the time-point of the assessment.
Otherwise you are influencing voter's decision.
If the outcome of this evaluation results in a change of the reward level (upvote, downvote, removal of a previously given up-/downvote) it is supposed to influence the assessment of the subsequent curator.
I guess I forgot about curators, so yeah I' d agree with you that payout is necessary for curators but curators votes for stuff that are going to make them the most money not the stuff they like the most.
In a system where users votes for stuff that they like payouts is not necessary.