Their world is off limits to God, unless that god can be crammed into their predictable, naturalistic little box, where He does nothing unexpected nor out of the ordinary.
It's so much more comfortable when God answers to you, rather than you answering to God.
The “uncomfortable” part about facing God is that you know that there is a standard of morality, it “ain’t yours”, and you “ain’t living it”, and you will be held accountable.
Those are all implications of facing God, and something few want to do.