So what if rainforest soil is terrible...their main function is to sequester carbon and act as a carbon sink supporting habitat and balance terrestrial ecology.
That is more for "why it helps there in the first place" than any disparagement of the rainforests. That the soil is terrible is more reason to leave them there - especially when they provide steady rain.
It isn't like temperate climates where you can rotate between farms, fields, and forrests over time easier.
