I hear this now and then - the claim that most people who call themselves Christian are "practical atheists". The reasoning is that people call themselves Christian, but they don't go to church very much at all and tend not to make decisions in their lives necessarily consistent with their church's teaching. Ergo, they call themselves Christian, but in practice they act like atheists.
Frankly, I think this is bull. In fact, I'd be tempted to say that most people - even self-described atheists - tend to be practical theists. They act as if there are objective moral standards, even if they violate them at times or disagree on those standards. They act as if life has purpose beyond what we personally assign to it. They act, even think, as if the future is something more than oblivion. Put another way, a person may be a practical atheist in one situation or with regards to one attitude, but a practical theist in another situation or attitude.
Though the truth would be that labeling people as 'practical atheists' or 'practical theists' seems useless for the purposes of gauging actual belief, inclinations, and potential. It's a way to roughly and imperfectly evaluate one aspect of a multifaceted query.