If I tell you I’m your god and you should give me all your money or you won’t go to heaven, you will rightly call me a liar, even though you can’t really prove that I’m not.

You won’t say “oh I guess there’s no way to prove he’s not god, so I’d better give him my money”.

In science, the default stance on something existing is that it doesn’t, unless there’s solid proof, or at least a compelling scientific theory suggesting that it does.