I was having a discussion elsewhere on the internet about why people believe and why people don't believe in god.
I am of the opinion that people believe in god, not for evidential reasons, but instead because they have some emotional feeling that god exists. No amount of logic will make someone like this stop believing (any more than trying to talk someone out of being in love).
The same goes for athiests. They don't 'feel' gods presence and so going to their door week after week is a waste. You can't force someone to feel something, so almost no one ever changes what they believe.
It's why the god debate will never end.
It makes me thing of the old question from an athiest to a Christian, "what would make you stop believing?" for most christians the honest answer is... Nothing.