Another reason might be that modern addictions and cultural vices have not been around very long in an evolutionary sense. The bulk of human evolutionary development occurred while scavenging savannas for nuts and tubers and carcases. There probably wasn't a whole lot of drug addiction going on back then.
Evolutionary biologists, though, have isolated some human behaviors which survive as relics of our hunter-gatherer past. Almost all humans, from all over the globe, have an innate desire (that's right, we're born with it) to eat sweet food, and fatty food. Why would natural selection produce such a result? Well, to live through the winter, or the rainy season, or the dry season (circumstances of local climate and ecology, of course, vary) you need stored fat, and to get moving when you need energy now
, nothing is better than teeth rotting, diabetes-causing, bad-fat storing sugars. When the human race couldn't rely on its food supply from one week to the next, never mind month after month, the ones who survived to breed were the ones who packed carbs and stored fat. Since humans become reproductive by fifteen years, at the outside, the deleterious effects of eating too much sugar and fat didn't kick in until long after the individual begins reproducing. And, in fact, for most of human history, people just didn't live long enough to pay the price of their foolish addictions to food, drugs, sex, bad literature, low humor, etc.