"as a rule, these 'reasons' are never purely intellectual, but are due to the unbeliever’s general outlook on life." Yep. That's been my experience. Generally, they don't want to give up the illusion that they are in control of their life. Or the delusion that their life is fine. Or, they want to dabble in that little bauble that distracts them from real love. Or, and this is especially true among scholars, pride won't allow them to acknowledge that God is bigger than they are.
Oh, the webs we weave for ourselves to hide the truth of our finiteness and desperate need for real love.