It is interesting that you think "report as duplicate" is rarely used. It seems to me that it is very often used. In fact, it seems that it is at times used more liberally than it should be on questions that aren't really duplicates.
As I said, rarely relatively to the duplicate content. Liberally? Definitely not! Most people(which is understandable, I guess) don't want to lose the opportunity to gain some more rep, even if they know that the question has been already answered a thousand times. I am most active in the `python` tag. At least there, I could list way too many examples.
Oftentimes where I've seen duplicated content marked, the question suggested doesn't adequately or fully answer the new question, which may have an advanced or updated (or just different but valuable) slant.
Keeping only the first iteration of a question is seriously detrimental to SE.
I agree completely with what you say. Unfortunately you're talking about something completely different.
I'm not talking about all the instances of posts that get marked as duplicate, neither about those that are marked as duplicate when they shouldn't.
I am talking about those that should be marked, because for all intents and purposes are identical to a thousand other answers, but unfortunately they don't get treated as such.
The reason? Reputation farming plain and simple. It's not even something that's controversial. It's happening all the time and many people like me, voice their opinions, instead of seeking reputation points. That's all.
