Why don't Impoverished nation use One Child policies?
Looking at counties such as Bangladesh, India or Africa (the continent) the one major problem they seem to be facing is their economy simply can't catch up with their population growth - there are not enough stable jobs to feed even a majority of the population and most people seem to be barely eking some form of meager existence on the fringes of functional society. If those countries put the brakes on their population growth, investments would over time lift enough people of poverty so those countries could start functioning again instead of drowning in hopeless poverty?
China's One Child policy, despite popular opinion, has achieved it's goal to curb population growth until extreme poverty was eliminated, and China was Africa levels of poor entering the 90s. Now that economic growth has caught up with the size of their population the One Child policy has been removed and they can now keep growing naturally.