Although the opening post may sound harsh, but its true. If this trend follows then possibly cell phones will no longer be sold with charging adapters as well.
Apple can do the same with their iPhone because we all know there's a shit ton more iPhones sold than all the Nintendo DS/3DS line combined. There's so many electronic products that uses the standard USB charger and hell more people have spare USB chargers lying around than a NDS adapter.
The point comes down to the fact that everything physically need to use the product is in the box. First it's the AC adapter, but then next will be Nintendo's home console to not include adapter and HDMI wire? Screw DLC micro-transactions, companies are going to start doing that with accessories you need lol.
Some people complained about PS3 not including HDMI wire,(well the Xbox 360 didn't even have an HDMI port lol) but at least the PS3 still included an composite av wire so people were still able to use it. (which at that time there were still many people that have standard tv and havent transitioned to HDTV).