Dunbar (famous for the "150 friends" rule, based on neocortex size) claims that religion is a scaling technology which allows groups to expand above the 1500 person size, which is as large as a group can get and still have most members able to recognize members by face.

Above 1500 people, a group needs a non-personal method to tag who is trustworthy and who might be plotting you harm.

Religion fills the gap nicely, gives you a reason to trust the other person. Works well, until it doesn't.

Long way of providing scientifically derived support to your statement on the "purpose" of religion.