To a religious person both our present and future life is wrapped up in the belief there is God who determines what happens here and what happens after we are dead. The god runs everything.
If there is no god, who runs all of this? What happens to life at this moment and after we are dead?
The atheist just shrugs at all of this. It is self evident people can regulate themselves because that is what they have always done. Religion was introduced to justify what humans had already decided. Thus, humans have always regulated themselves and they always will.
What happens after we die is also self evident. Nothing happens. We are all dead. There has never been a shred of evidence there is any "life" after we are dead.
Often religious parents are distraught on the news a child has left the faith. They think the god they believe in is necessary for their child to have an afterlife. I can't begin to remember how many such parents I have known.
A generation is now moving into adulthood in which the majority does not believe in a god. Most of the continent of Europe has lost this belief. What can we expect to happen when only a minority of the population believes?
If what I explained above is correct, that there really is no god and humans made up their own rules and attributed them to various god, then nothing will happen when the majority loses interest in its gods. Things will just go along as they have since the beginning of humans.