It is the short-sighted way politicians work. They think about their term in office and not about the longer future. That's the nature of humans, unless their personal interest (e.g. Family) is concerned. Perhaps the people of the world should be directly involved/asked...

The best analysis for the failure, I have seen is made by Benito Müller from Oxford Institute for Energy Studies: It is all too tempting to blame negotiators and UN procedures. Yet the single most important reason for the events in Copenhagen is what happened before – namely, the lack of political will and leadership during the months leading up to the Conference to engage in real negotiations. The lesson that all attending leaders should take to heart after the Copenhagen Summit is that it is impossible − even for world leaders − to make up for months and months of wasted time in 24 hours, no matter how frantic they may be. link text