I believe the Gods are necessary to human kind. Without any belief in something above pulling the strings, humans would have nothing and/or no one to blame when things went a-wire. Also, Gods give humanity hope that there is a reason why we are here, and/or something after death for human kind.
The concept of God started with our early ancestors thinking about how nature and the world surrounding them that they had no control or reason for why it was that way. A lot of beliefs in religion, that exist because of their beliefs in God or Gods, often sponsor charities and other events to help better their communities and/or the world.
Also, without God(s), many people would not have a lot, if any, reason to live this life with any purpose. As often times believing in something higher up than you and/or that they are working towards something, they will try their best to accomplish all they can in the little time they have.
Going to places of worship can help people cope and/or get over addictions.
Imagination has nothing to do with it. Belief is what religion is based on, yes, but belief is what gives people hope. And without hope mankind would be desolate, in some sort of dystopia in which no one is truly happy and no one has a reason to live. So while it may seem silly or ridiculous to some, it is important to believe in something, and God(s) fill the void needed for beliefs so that everything is not meaningless. Because a life without living to some is not a life at all.