Why are posts with bid-bot upvotes downvoted in the Steem community?
Because nearly all Steem front ends afford the greatest visibility to the most highly rewarded posts. Imagine for a moment that you could bid for a vote and get a vote worth just as much or even more in return regardless of the quality of your post.
Then buying votes would not only get you attention for free or even pay for it while getting your post attention to boot. A lot of users would be buying votes and the vast amount of stake that bid bots possess would be doling out content-agnostic votes day in day out. A shit show of poor content occupying the top spots in Trending on Steem front ends would ensue while quality posts with no bought votes would suffer from a lack of serious stake voting for them.
This is what Steem had prior to HF 21 and it wasn’t a pretty sight. You could call it a failure of Proof-of-Brain, which is the who reason for being of the content reward pool in the first place.
What we have now is MUCH better. Former bid bots saw their former business dwindle and became curation projects. Many of them are constantly looking for decent content to upvote for free! This is how it should’ve worked all along.