Well why do you think flat earthism persists? hur dur evolution!!!

"Persist" is a funny word to use when you're talking about human history on an evolutionary level, seeing as how we've evolved very little from our conception in Africa only a few hundred thousand years ago, practically the blink of an eye on the evolutionary scale. Even if religion has been around from the beginning of our species, it hasn't really "persisted" very long at all.

As far as religion's "use" in an evolutionary sense, the only thing that evolution selects for is more babies. If you have more babies than your peers, you're more evolutionarily "fit," it's that simple. You could then say that religions that encourage their members to have more children are useful, but again, that's only if you think the most important thing in the life of a human is for them to have more babies. Most people would say other things are more important when it comes to human life, which would make evolution useless as a metric to determine the "use" of religion.

People not following any particular religion get laid at roughly the same rates as followers of religion. So there would be no evolutionary pressure involved there.

It was, but we've outgrown it

The mark of civilisation is to be better than our base nature

Religion has had its day. Now it's all about power and money (it pretty much always was, but I'm trying to be generous)