I stopped using most bots after the HF because - if I'm not making a profit, I at least want to come out even.. and that doesn't happen now with many of the bots unless you pay large amounts of STEEM, and I was only paying the bare minimum for votes.
After the HF and taking out curation, many bots are a loss.. However small a loss is a loss.
I suspect it is a bad ROI that has decreased interest in voting bots, more so than fear of downvotes, to be honest..
It's probably a mix of both. Not much we can do about it, but it's likely we'll eventually shut minnowbooster down. We want to focus on services that benefit the community more, like TokenBB, GINAbot, and DLease.