I think Radimus has got most of the reasons.

Of course it doesn't help that the search mechanism is broken.

A search for "mingw" in all forums should return 4 topics, as that is how often I've mentioned it.

In fact it returns 46. How many unrelated or irrelevant posts would you read before deciding that the search mechanism was not the way to get the answer?

I don't think we get too many repeat offenders. Usually it is a low count poster, who in their naivety haven't considered searching. Once they've been put right they usually behave themselves.

I'd have to hold my hands up to being directed to existing posts when I've queried something that I thought was obscure.

It is sometimes irritating when it happens for the tenth time in a row, but I wouldn't let it ruin your day.