A lot of people don't go to church because other things have taken the place of church. It may be that people once went to church, but now hold back because they may feel unwanted or unworthy. Unchurched people may not agree with what they consider to be man-made rules of institutional religion. Some folks I've talked to don't participate in organized religion because they feel that life has crushed them. They feel defeated and disillusioned.
Life feels like a cruel joke, without meaning and without goodness.
Besides, so many times the message sent from churched people sounds like it is for winners only. The religion of America is not for losers. This is a religion of sad news, bad news, - certainly not good news. The law, for those who are failing in their own eyes, is a monster with a cruel whip in its hands. Two men went up to the Temple to pray, one a Pharisee and the other a tax collector.