I lack the belief in the existence of god/gods because there is no evidence for such entities. I think it is possible that god/gods exist though I think it is unlikely.
Think of a mythical beast that you think may have possibly existed at one time. I'm not mocking here, just trying to draw an analogy. Your opinion on that beast would be similar to my opinion on gods. Sure their existence is possible but, until there is evidence, I will lack the belief.
Belief does not require evidence. That is the definition of it. Once you have evidence you don't need belief.