I just don't understand how someone could believe religion could be useful, and yet not believe.
In my case, I actually believe religion is often not useful (indeed, I believe Christianity, as practiced in North America, is mostly harmful), but I'm inclined to believe in God anyways. But increasingly I realize the God I believe in is more like the Hindu Brahman than the personalistic theism of the average evangelical Christian.
The benefits of religion are largely illusory, which is why I believe the "nones" are growing. The main reason people were religious in the past was social cohesion, networking, a sense of purpose, and so on. Now days we have facebook and the internet, more involvement in work and careers, and so on. We get more of a sense of connection and purpose through our families, especially with fathers spending more time with their children and spouses. And there's a huge tradeoff in accepting Chrisiatiy, such as accepting an ethic that most of the modern world has rejected, endorsing everything from the subjugation of women to contempt towards gays, to say nothing of the fact that conservative Christianity frequently goes hand in hand with an apologetic for capitalism and economic exploitation.