The three interrelated goals of ecological economics are sustainable scale, fair distribution, and efficient allocation. All three of these contribute to human well-being and sustainability.
Distribution has many different impacts, not the least of which is its impact on social capital and on quality of life. We find that if the distribution of income is too big, that creates competing groups within society. You lose cooperation. There is actually research to show that more unequal societies are less productive in the end because they spend a lot of their energy trying to maintain that gap. So distribution has a lot of direct and indirect feedbacks on how the society is actually functioning that the conventional view tends to ignore. It just focuses on having more, the idea being that the more we have the more we can spread around. But I think we're getting into a time where we have to worry about distribution. We may not always have more to spread around.