People do want to benefit themselves, but nobody wants to thinks of themselves as the bad guy either. In the simplest case, they invent a justification where their actions are actually positive or they're a victim, in more complex cases they tell themselves they're doing something for an innocuous reason even though there is a huge moral hazard and self-interest ends up winning.
And an ignorant, unstructured, or illegal approach to benefiting yourself often hurts other people.