I don't think people object to de-duping true duplicates. The problem is near duplicates, where the original question/answer didn't quite cover what you're asking. In those cases, it can be frustrating getting past the SO duplicate filter, which can sometimes be too aggressive.

Or, when searching for answers, you keep chasing your tail because the mods kept killing off the variants of the question you cared about, and you have to cobble together answers from the comments because those will often be all you get.

Or (and arguably worse), you'll find a relevant question but the answers are inundated with "like the real answer, but variation for situation X" because people are posting to the main question because they know the almost-but-actually-not dupes will all get closed out.