Evolution just hasn't caught up with our civilization
We're still Cromagnons with car keys. Our biology hasn't realized that
we don't need to reproduce a lot any more to have enough offspring
that survive to reproduction age.
As with many things, humans will have to change radically to solve this
problem. But I think if that happens, we won't even be human any more.
That may not be a bad thing, though. Because otherwise we cannot
keep going the way we are and expect things to last here.