Fascinating. Of course to me it implies coercion or "faking it." Perhaps they could be open to reason and be reached if they had a little more confidence and some encouragement.
I also wonder about those who have trouble coping with guilt, or are afraid, or desperate.
Another reason is they don't know there is other alternative. This is my case. I live in a place where > 95% are religious, so I've never thought non belief as a possibility. When a fav band member said he was spiritual but not religious, that's the first time I saw there is alternative.
Another thing is the internet. It has given a voice for the atheists in my country. My bet is there is a significant raise of nones in my country.
I wonder what that breaking point generally is? Could it be the pressure of keeping up appearances that are not heartfelt, or feeling separated from friends and family who are not devout? I suppose it's different for each person.
I live in a multi-religious environment, it has never really bother anyone. But islamic radicalism is on the rise and they spread doctrines that didn't seem come from an all loving being. So, the critical ones are forced to reevaluate their belief.