It's been a long time since Nintendo released a title for the 3DS, but they have been manufacturing more units of the portable for sale around the world. Now that manufacturing run has come to an end.
Nintendo has announced that they're officially ceasing production of the 3DS family of devices. That includes any device in the 3DS family, such as 2DS, New 2DS XL, and so on. Whatever is available on store shelves now is all that there will be. If you want to add one of the portables to your collection, now's the time to do so.