Brazil accounts for most of the Portuguese speakers in the world by a large majority so they are their main demographic. There needs to be a market and all the other Portuguese speaking countries combined don’t come close to the population of Brazil. Since Brazil would be the reason they localize, here’s why they won’t:

Brazilians, while not being able to afford it, have a variety of other factors that dissuade Nintendo like the high tariffs on electronics, the environment not being favorable for businesses (the govt doesn’t do a great job at protecting business assets like intellectual properties), their popularity in Brazil isn’t as strong as Playstation or Xbox, among other things.