I’m relatively high-rep. I don’t have any issues with stupid or duplicate questions, they don’t waste my time. Nobody forces me to answer every question asked on SO.
You know what is a waste of my time? When I wrote a good answer to a question which I think is fine, which then goes to oblivion because some other people, who often have absolutely no clue what’s asked, decide the question is not good enough.
First of all, there's often a subtle difference in the questions despite being flagged as duplicate. And pretty much as soon as it's flagged, other people are all to eager to use their vote close power, taking a disproportionate amount of energy to try to convince them otherwise. Frankly, the few times I've tried it feels like trying to argue with someone that thinks the earth is flat or the moon landings were faked.
Secondly, sometimes I like answering questions. It's a form of teaching, which is really a form of learning, and writing a good answer gives me a chance to learn something in more depth in order to be able to explain it. I don't really care that a similar question has been answered before, I'm happy to focus on the subtle differences and specifics of this question and try to make a good answer.
However, too often your reward for this is a closed and then deleted question, which is kind of like a punch to the gut.