lol, I think the same phrases appear about a hundred times on google without a mention. the problem that we have is that plagerism only seems real if it can be googled (or in our case if we know the text quoted). Text from books could go unnoticed for months unless an editor smells a rat. Four sentences from a Wikipedia article (albeit follow through sentences) have shook enough people to respond, how about if four verbatum sentences from a book were posted in wikipedia? would we be shocked at the copyvio?
Plagiarism is real and (as far as I'm concerned, and I would imagine pretty much everyone else) seems real regardless of the source, it's simply very difficult to spot when it's from an unfamiliar offline source. If we found out about four sentences in a Wikipedia article copied from a book we would immediately remove them, we're just quite unlikely to ever find out, which is unfortunate, but unavoidable.