What are you talking about, alcoholism is a classic rampant poverty addiction?
>there were hardly any addicts among peasant communities in rural third world countries back in the 70's or 80's.
Are you sure the assertion is wrong?
How do you know?
"I grew up in a rural setting in the third world," would be a great answer.
But even putting that aside, gluttons, drunkards, and gamblers are certainly ancient and well attested, certainly in the western (abrahamic/hellenic) tradition. Perhaps there are some societies without this but it not poverty or want or lack of abundance that provides relief.