Ugh, that is just flat out poor.

Yes. The Wii was the most recent one. 

Well North America is a very expansive region for one, so producing the needed units to stock stores would have been quite costly.  Plus, we don't know the division between 3DS and XL.  In Japan, the XL won handily, but the standard still sold respectably iirc.  I don't know the EU's division.  In the US it might have been much more lopsided.  Also, in Japan I think it's obvious they were anticipating capturing some people with the faceplates and accessories for the standard N3DS that might not otherwise pay attention.  However, the failure of that push to even out the sales between it and the XL model likely influenced decisions abroad.  I honestly wouldn't be surprised if the N3DS comes to the states later, maybe this Holiday, because they don't want to launch it now in the shadow of the XL model and during the slower February month.  Also, they said later they want to target a younger audience more directly and the N3DS standard would make sense for that, especially during the holidays.

But I think most of this is down to keeping costs of production in check.  The standard 3DS did very poorly compared to the XL model and they don't want to burn resources to supply a region with the new model right now when the sell through could be bad.  If they do launch it later during the holidays, they can capitalize on the rush, especially the influx of parents buying for children who are easily swayed by price differences.

Because some people prefer portability over screen size, some people want the customizable faceplates, and for some it's the principle. Many people don't want choices made for them and the fact that Japan, Europe and Australia are all able to make that choice for themselves makes it seem like a slap in the face. If they got rid of region-locking this wouldn't be as big of a deal.