Keep this in mind too: Star Trek, while originally attempting to portray humanity in the future, inevitably created canon. Thus, there is a world war 3 in the star trek universe that occurs around 1999 (I can't remember the exact time frame). So It makes sense that 20 years after the world "ended", people would be pretty scared and do anything to try to right civilization.

In the end, as the original post implies, Star Trek is no longer a vision of the future, but rather a sandbox to put humanity into and see how they react.