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
Each gain stage inverts polarity. A phono amp generally needs 2 amplification stages for gain and RIAA and an impedence matching buffer stage to drive the power amp. 3 stages = inverted polarity. 3 stages are better than four -less is more- so they leave polarity inverted. I believe they leave it like that for 2 reasons. It works fine with their amps. It doesn’t make a big difference to SQ.
Now my question is...why? I would say 98% of buyers of this amp do not know to reverse the cable connections
That is because they do not read the manual.