it's hard to see.
Some possible reasons why people don't care as much as they should about the environment, in general...
1). It's hard to see. Most issues are not 'tangible'; they do not (yet) affect most average people on an everyday basis.
2). There are innumerable variables to account for in making any study or prediction about environmental phenomena, which in itself tends to make the whole field seem rather abstract or arbitrary in the minds of many.
3). Related to (2), corporate money no doubt plays a role. Some, or perhaps all large corporations, for which tighter environmental regulations would cut into their profit margins, employ well-paid scientists to exploit the inexact nature of this science, selectively tweaking their variables of choice or perhaps just fabricating data to make their studies come out in the company's favor.
4). It seems most of the world's population keeps itself on a "fear diet", mostly courtesy of their leaders. If the masses are perpetually led to believe that "The Enemy will come over the wall and destroy you within a year or two if you don't act now", then what relative place in their thinking or priorities will claims of environmental blight thirty years hence occupy?
We should care, but we don't, for the most part, unfortunately.