Voting just influences the rewards distribution, but there are many motives for deciding what you vote on. Should it matter? We have downvotes if we think it is not justified, but we do not necessarily know the relationship between the voter and votee. If it really is votes for trash then go for it. I mostly vote manually so that my votes go to what I think is good, but I may favour some friends more than those I don't know. That is human nature. The important thing is to use your votes, preferably having seen the post.
For now Hive is a pretty small club with various communities. If it ever gets to millions then the dynamics will change.
True. Eyes on curation is what makes the platform better so hopefully everybody tries to put in their fare share of it.