The reason is the text of the questions, which is what people type into the Google search bar. Documentation never has questions worded in the way people would commonly ask it.
For this reason, I wish they would allow redundant questions to be asked, if the phrasing is even slightly different. But the rule-mongering mods always remove it if they can.
In general, no: most duplicates stay around. Having multiple copies of the same question with different wording is useful as search fodder, because people looking for an answer may use different wording too.
That's good to see that they actually have the right rules, but I've used it many times where my questions were closed simply for appearing similar to others (when I did not even find the others in my search results). I suppose the mods can be overzealous.
For this reason, I wish they would allow redundant questions to be asked, if the phrasing is even slightly different. But the rule-mongering mods always remove it if they can.