The quantity of self-described religious adherents who don't go to church, don't pray, and don't think much about the afterlife (until the due date visibly approaches) is frankly quite large. Belief != fervor. And, proportionally, there's quite a few places dedicated to bringing atheists together and promulgating their beliefs (tax exempt by the way).
As humans, we seek explanations, stake our identity in our beliefs, and pursue fellowship with those who share them. I know of at least one secular group in my city that explicitly claims to be a church ("The Church of Beethoven"). There are definitely distinctions between believing in historically established religion and believing in some form of modern secularism. But atheists like to phrase it as "We don't have any of the pitfalls of religion because we don't have religion" and it sounds an awful lot like monotheists claiming they don't have any of the pitfalls of being pagan.