Why do some manufacturers reverse preamp polarity in the first place?


My Rogue RP-5 reverses polarity, so I switch the pos / neg at speaker terminals. The manual does not mention this, however, I wrote the company and they the amp does reverse the polarity. 

Now my question is...why? I would say 98% of buyers of this amp do not know to reverse the cable connections. I would say most reviewers did not as well. Yes, I realize, polarity reversal is not noticable in most instances. Especially, since many recordings are all over the place when it comes to polarity (at least that is what I've read).

So the question remains...why...why not just have the amp terminals set up so the buyer can just plug in as normal?
aberyclark
He does and presents no evidence whatsoever. He came into our room one time and insisted that our room was in reverse polarity. I flipped the polarity switch on our preamp. Then he insisted that you couldn't hear it on LP- only CD. So I played the same track on CD as I had it on hand. Then he insisted that you couldn't hear it if the source was analog...
And then he left the room hastily, leaving behind only our impressions of him, with which we made jokes from for the rest of the show. 

Thanks Ralph - priceless!  
Rupert Sheldrake was a respectable biochemist and plant biologist before he became a parapsych crackpot. PEAR is debunked.