My opinion is speculative and not well-informed, but if I had to guess I would say 1) our governments are more or less defacto oligarchies (or at least the politicians are generally on the upper end of the economic spectrum), and 2) because of many social factors this seems to be a real uphill climb, so I can actually sympathize with politicians who on one hand have maybe a vague sense that they won't suffer the worst effects of climate change and on the other don't necessarily have a clear or great path to produce the needed changes.