Why do journalists hate PRs?

Yes that old Chestnut. I've just been directed to a Scottish journalist's blog by the wonderful Passionate Blog which proceeds to diss the public relations profession with Why Journalists Hate PRs - and Why PRs Hate Journalists.
Amber has some interesting points and some real stinkers from PRs who, in their enthusiastic response to her request for information on house builders across Scotland, sent her... well, a load of shite!
But I suspect she doth protest too much and that there may have been a few nuggets of genuine interest in her inbox that she found quite useful.
Maybe standards have slipped. When I was in full-time journalism I have to say the standards of press materials was very good. Usually written by an ex-hack and answering all the who, what, when, where, how questions. Generally it was ready for print.
But journalistic pride (not professional - journalism is a trade not a profession) forebade us from cutting and pasting it into the paper. At the very least we'd want an interview with the chief executive, a decent picture or another angle if it had gone out to rivals.
And if it was a bad press release - usually from a London agency by someone called Jacaranda or Arrowminta - we would politely tell them and explain that we were usually looking for a story.
The curiously thing is that now, on this side of the fence - where my company adopts the same rigorous standards as when I was running the business desk - many journalists use the press release verbatim with their byline, do not challenge any of the content and do not request any interviews.
I'm exaggerating of course - as I suspect Amber is - and this doesn't happen all the time but regularly enough to prompt concerns.
Back to the orginal headline - the real question is why do journalists need PRs - and why do PRs needs journalists?