These are the reasons I can think of:

- The problem dimension is hard to visualize for most people. Similar to space distances are hard to understand.

- There's nothing an individual can do about it other than trusting their local institutions and voting. Recycling, being a rational consumer, choosing greener options have negligible impact and it's main benefit is making people feel good.

- The consequences are slow to materialize. Sure, it's a bit hotter or more rainy in some places. It'll take a few more of these for population as a whole to feel inclined to become more involved in the matter. Which might be too late.

Either way, not much to do about it.