The pessimistic reason is that we are still enthralled by the unparallelled growth and prosperity we have enjoyed for last seventy years and got used to it: But the next seventy may turn out to be very different. We may not return to the dark ages and may not have to fight world wars, but we have to get used to deceleration of growth. Our political ideals, including the current extreme rhetoric, are all built around the idea of economic growth: We need to think differently, perhaps more compassionately, to live with this new reality. As we may hit the limits of growth, perhaps imposed upon us by the climactic constraints, we have to come to accept that lack of growth is no one's fault, and we just have to live with a little less, constrain our desires a little more. For this, the progressives may indeed have the best answer.
Indeed, such a politics still remain without its manifesto, parties and leaders. But such a message is emerging: Read Steven Johnson's Future Perfect, Mariana Mazzucato's The Entrepreneurial State, Sudhakar Ram's The Connected Age or Marina Gorbis' The Nature of the Future, and you will see a doctrine emerging, a demand for a new kind of capitalism, which mixes the entrepreneurial energies with compassion, going beyond selfishness and consumerism, as well as grand schemes of social engineering. The politicians may not be listening to these voices, but it seems a matter of time that they enter the mainstream.