You're implying that most users just go with the flow and are unable to determine the value of a question for themselves.
I beg to differ. Most users don't vote at all. Those who do vote do it for a reason: either the question is good or useful to them, or it is useless and they believe it should be marked as such (and that this should be made clear to the asker).
In my opinion, not enough of the bad stuff is getting downvoted given that every time I load SO and click on several random questions, a worryingly high percentage of them turn out to be zero-effort debug-my-code-for-me/write-my-code-for-me/read-the-docs-for-me garbage.