Why do Athiests require 'proof' that God exists?

[Annik]

I can shoot watermelons from my tits. I won't show you under and circumstances, but I can do it. PROVE ME WRONG.

I can't prove you wrong and I accept that. However I do have serious doubts - biology and physics say its an impossibility.

Your god is as unlikely as my watermelon-cannon. That's why we need evidence. You'd say I was crazy or an idiot if this was said to you out of context. It'd be a bigger issue if people wasted their lives worshiping my tits (not that they don't, ey-ey~!).