I think it is fun. You say in the OP to disregard them as collectables but that's an intrinsic part of the appeal.
Like, I bought MK8D, pulled out my amiibo, and scanned them to get a bunch of costumes. I had the figures anyways - I didn't buy a Pac-Man figurine for $10 in order to unlock a dumb Mii costume. I don't even race with Mii all that often. So I had got a cute little bonus for free because I bought something I wanted anyways. And in this case, the only way to do so is by interacting physically.
Like, when a game gives you a little bumper sticker for having save files for other games on your console. It's not saying "rah rah, spend $60 to get this bumper sticker!"
Like, I bought MK8D, pulled out my amiibo, and scanned them to get a bunch of costumes. I had the figures anyways - I didn't buy a Pac-Man figurine for $10 in order to unlock a dumb Mii costume. I don't even race with Mii all that often. So I had got a cute little bonus for free because I bought something I wanted anyways. And in this case, the only way to do so is by interacting physically.
Like, when a game gives you a little bumper sticker for having save files for other games on your console. It's not saying "rah rah, spend $60 to get this bumper sticker!"