Because nobody listens to the scientists. You have two sides where one side thinks we should sacrifice (all) economic growth for the sake of the planet and another that thinks we should sacrifice the (entire) planet for economic growth. The future will hopefully look nothing like either of them. We should find a healthy balance between the two and that means we need a self regulating system and preferably it should resemble something we already have. Landfills charge for disposing of garbage so why not charge for atmospheric pollution? It already exists and is called the Kyoto Protocol.
In the US many (most?) prominent members of the Republican Party (our right wing/conservative political party) deny the existence of global warming/climate change.
There was a NYtimes article showing that the denialism has been happening in all three english speaking countries: US, England and Australia, because of brainwashing.
Of course, nobody wants to hear they are the useful idiot that fell for it, but we can't let that stop us from pointing out reality.
As far as the Republican party goes, I'm sure there are many who do believe in climate change, however they have to fall in line and so they will not speak up. The Republican party is known for presenting a "unified" message.
