Anyone remember the hoopla around the time of the launch of the 3DS about how doctors warned against possible ill effects for very young children? That's obviously who the new model is designed for. The lack of a hinge helps durability, and you wouldn't let kids that small take something that expensive to the park, so portability is not that big of a deal. The repositioned controls make the device less top-heavy, which is also easier for weaker hands.
Don't rage about the design, it's not for you anyway.