I’m really curious what makes you think that? I for one would be very happy to play a port of Zelda on my smartphone. Do you know how many fans would love a port of Pokémon for smartphones? Making a move like this will also produce a massive boom on smartphones gaming accessories. Nintendo loves selling accessories.
Even tho I agree with you, as of this writing Nintendo gains more from hardware sales. But if they decided to port their games to smartphones its given they’ll sell millions in a couple of days. The only thing stopping them is their pride.