There's a bunch of reasons. To throw one onto the pile: because carbon emissions are an externality that the Invisible Hand seems to be having a real hard time

There's a bunch of reasons. To throw one onto the pile: because carbon emissions are an externality that the Invisible Hand seems to be having a real hard time suppressing, it sure seems like - and this is how it's gone so far, and there's a kind of cultural consensus around this - that the only way out of this could be be pretty heavy-handed government intervention. For, similarly, a bunch of reasons (see "The Californian Ideology" for a start) there's a strong inclination in tech circles towards anti-regulation, anti-government, neoliberalism and/or libertarianism. So those two things are colliding head-on: when their ideology encounters a problem it can't solve, people often care more about their ideology than solving the problem. It's easier to deny the problem exists than to restructure their views.