I think it is important to recognize that when someone is that deep into depression, their vision, their perspective, has narrowed to such an extent that they don't usually think about being selfish. I know I never did. None of the people I've worked with ever had the goal of being selfish. To think about being selfish would have required a different capacity of thinking that was, quite simply, beyond our ability.
Think of it as a horse with blinders on. Extreme tunnel vision is another way to describe it. As our emotional pain escalates, the rest of the world ceases to come into our awareness, much less our focus.