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.
Should duplicates be deleted?
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.
https://meta.stackexchange.com/questions/10841/how-should-du...
It's not due to some Google-fu though. People ask questions (on SO) in the terms they think about problems. But documentation is written according to the structure of the thing being documented.
So SO ends up being a more direct mapping from problem to solution. Google simply captures what's there (in both cases). It's certainly good to consult the authoritative docs in many cases.
besides, google is a knowledge base index, if you want to search a documentarion website you can both both inform google via site: or use the docs own search system which most have as of today
For simplified example, if you want to find out what flag -wtf does in some unix utility, the man page would be useful; but if you'd want to find out which flags should be used to achieve WTF then you'd often need to read the whole documentation to find out - stackoverflow serves as a "reverse index" in this case.
When you don't exactly, SO is a good pointer to the part of the documentation you didn't know.
I'm sitting at a bar in Turkey. I want to know how to say, "I want a beer," in Turkish. I know how to order a beer, drink the beer, and pay for the beer; I just want to know how to do it in my current circumstance.
How many times have you read docs and thought "well that's relatively straightforward" just to end up googling an error message 10 minutes later and end up on SO.