It seems that many people today who never have kids do so for a good reason, such as unstable personal economy, not owning their home, not knowing as much as possible that their future children will have good lives.

The people that continue to have kids today are often the overly religious, the financially or generally irresponsible who lack self awareness, or just plain stupid people. These are not traits we want to evolutionarily select for. See the movie Idiocracy for an example.