To use the gravity analogy above, you do not necessarily need to understand it - you can prove it exists by dropping a plate or trying to jump off the world. You cannot prove that any one of the certainly thousands and probably hundreds of thousands of gods and goddesses humans have invented ever actually existed.
I didn't say that we need to understand gravity. I was using it as an example of faith. We assume that gravity will continue to operate without ever understanding why that should be true. Dropping a plate today does not prove that that effect will be unchanged tomorrow. We have evidence that it has operated unchanged for many years. We assume that what is happening will continue. We have faith that gravity will continue to operate.
We have evidence and proof for lots of things indirectly by the effect they have. Why would you deny that sort of evidence or proof for others to believe things that you don't?
You say "cannot prove" on the basis of your own position. Lack of understanding, evidence or proof does not constitute total certainty that something does not exist. That is a decision that you have made. Others make a different decision on the basis of the understanding, evidence and proof that they have.