Because it is not really about the science. What people differ on is the level of moral responsibility we hold. Some people simply reject the moral imperative

Because it is not really about the science. What people differ on is the level of moral responsibility we hold. Some people simply reject the moral imperative to protect the environment. And science does not help in that argument. You cannot scientifically prove that someone should care about a moral issue. They have to understand at a more intuitive and emotional level first. This takes time and is messy (see every contentious political issue ever).