This is a really good question. I think what you have to keep in mind is that you can't apply what we do nowadays as to why the right seat is the way it is. People were flying helos long before any of our modern day machines were around, including the tandem ones. It's also interesting that as many knowledgable people we have here, as well as on that other board, no one really seems to know the answer, for sure.
The idea that it allows you to keep your hand on the cyclic at all times sounds reasonable to me, since it all started in the days before trim and AFCS. As Skid is saying, in the fleet, it's not as big a deal to always have a hand on the controls, at least on the Navy -60 series. That's not to say you shouldn't be guarding it, but if you're up and away, and need to mess w/ something for a few seconds, taking both hands off the controls is not a big deal since there's an Alt-hold, trim, and AFCS flying for you. You guys will be pleasantly surprised when you come from the seemingly spastic -57.
@Schnugg:
I know your question requires people to think outside of the box, but personally, I would not want an NFO next to me. I know similiar things can happen in fixed wing land, but a helo is just so dynamic that if you need the second person to take the controls, I would prefer that to be a pilot who can get me back to the boat and on deck at night.