The active install base of the 3DS must be super tiny compared to what it was years ago.Software sales last quarter (ten of thousands):
3DS: 295
Switch: 1796
If the total install base ever made sense past a platform's prime we'd still see games being published for the PS2 and DS.
People need to stop this nonsense, whining about people wanting more Switch games, crying about "elitism". Many consoles have sold out the ass and they didn't just keep making (big) games for them years into their successors lives just because of that. The Wii was pretty much killed off when the Wii U released, so why is it ridiculous that people are upset about big 3DS games being released nearly two years into the Switch's life? I understand that this particular game uses the DS quite a bit, and it's also not a third parties obligation to make sure the Switch has games, I'm more upset about first party games being released on it, especially when the advantage of the Switch was to have all of Nintendo's devs on one console.
Honestly it sounds like the usual whining you see every generation when some people refuse to upgrade to the next gen consoles and want everyone else to be held back because of them. The 3DS had some great games, but I am beyond done with that weak ass hardware, and honestly I'd never been a big fan of the second screen in the first place.
For real, the 3DS hardware felt like it belonged to a past era in 2012, I can't imagine using that thing in 2018. More Nintendo games on Switch means more reasons to buy the system, all these late ports and indies I played on PS4/PC do nothing for me.