Why do Athiests require 'proof' that God exists?

[Darwinian]

I do accept that I can never know if God exists or not, just as I employ the same principles with the tooth fairy, Odin, Zeus, Ghosts etc. etc. It's just that I find the complete and utter lack of any evidence, credibility and verisimilitude overwhelming.

Good point. However the tooth fairy is a little woman with wings, not an ineffable, omnipresent being. Therefore we can prove if the tooth fairy (and the other things you mentioned) exists because we can look for little women with wings. We can't look for God.

Absence of evidence is not evidence of absence therefore you cannot prove that the tooth fairy does not exist.