it won't cost them any sales because they're Nintendo, but also amiibo sell like hotcakes anyways, you're making the game worse for no reason
and even if you buy the game and the amiibo, now you have to carry it with your Switch if you want to use the feature. they literally made the game worse
fucking Uvisoft's Starlink, one of the last toys-to-life games, doesn't have this limitation. You can play completely without the toys, just switching your config in the game menu. There's even some digital-only stuff included with the base game lol