the T-pose gives the easiest and most clear way to assign polies and vertices to specific bones when rigging. It's not a Poser thing (see maya, Max, ...) and it might even be outdated given modern rigging techniques. But old habbits never die. It might be the worst pose for doing anything else, especially muscle tones, although it proves a nice starting point for cloth simulation as it gives the least interference and folds.

There is hardly a reason to do it when the character is not intended to perform animation.

I can touch my left shoulder blade with my right hand, and vice versa. Does that count for anything?

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Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

visit www.aRtBeeWeb.nl (works) or Missing Manuals (tutorials & reviews) - both need an update though