Some of curation highlight post like the first link could take a hit, I really do not think they should bid bot them myself, however it is a method to get their list of what they felt was valuable content highlighted. Are these list worth the dollar amount they get? not sure myself. I have been put on a list or two a few times but have rarely commented back on the list. If they gave a real vote to my content then I would vote for them, but if it is just a look at my list help me make money off the backs of other peoples work then I completely by-pass it.
That being said they do provide a sort of service for people looking for content, so a couple bid bot buys and the rest all trails or manual votes, a very hard thing to see. I do not think automated down votes would work, there is just to much subjective stuff to evaluate.
That was bid on today too, day 6 of the post........
I know steemleo do not like daily curation ($) highlight or staking posts, they are easy to produce and from what I see do not earn much engagement.
Most of the ones I have ever viewed did not have a lot of comments, but they do get what look like a lot of real votes too, mostly trails I am sure. Until there is a click through feature we will never know if these curation, "Look at what I found" post are used or not. I know I have clicked a few highlighted post on various list, but not a lot, and I myself rarely vote on them because I try to vote on created content and assembling a list of links,..like you said...easy to do, so pretty low effort on their part.