I don't agree with the assumption that religion is obviously man-made. Another possibility is that religion is a response to something that is actually out there. Primitive societies' interaction with the spirits is usually fear of the spirits and/or trying to control/manipulate the spirits to get what they want which they are unable to provide themselves. One explanation is that they act out of ignorance. Another explanation is that they act out of some sort of knowledge that we have written off.

Furthermore, religions claim to have a revelation of truth not discoverable by the western, Enlightenment-based assumptions that the world consists of only the physical reality. There could actually be a spiritual reality, and one of the religions might actually be correct. For example, I personally think that the Christian worldview that we are all selfish (in opposition to God, who is giving, since he needs nothing) explains a lot of things: poverty, oppression, why we can't stop fighting among ourselves, why communes fail, among others.

Religion might just be made up; some certainly seem to be. But, it might also be that some are actually right, and if one of them is right, it might have profound implications on how we live our lives. For example, if there really is a God who loves us so much that he died so that we could eternally relate to him as a child deeply loved by a father, we do ourselves a disservice by assuming that it is just made up. Christianity might be wrong, some other truth claim might be right, but until we have established that religions do not reflect reality, we should at least remain open to that possibility.