I think the opening position evolved out of a desire for more interesting openings and resulting middle and end games. The position does seem strange at first, but it is sort of the foundation for more sensible positions, like turning 6-1 into a fortification of two pieces on the same space. Without the opening position, you would only have at most one checker on a space with this roll. I have absolutely nothing to prove any of this, it's purely speculation, as this is something I've wondered about as well.