I think its the the reduced functionality of the lite that takes away some its appeal. Like it's one of the main selling point of the Switch. Play how you want, portable, or on your TV. Take that away and you have a machine that just can play on that screen. Its not a substantial amount more for the full-fat package.
You also get detachable controllers with HD rumble and dock which doubles as a charger in the OG model.
Nintendo first party games always sell well in Japan. And like the rest of the world, their prices generally hold up and rarely go down.
Reduced functionality is lite only portable aspect. In short, is the missing stationary console aspect that makes the console sell less? Well ... case closed