As people are running around quoting themselves silly over Mr. Beiber's (noted for his spiritual knowledge... oh wait.) exalted "I am spiritual but not religious/don't need church" baloney - I'd like to remind everyone that Our Lord and Savior Jesus Christ did not leave us a Bible - He left us the Church. And if you don't have the church - you're deluding yourself into thinking you are keeping yourself on the 'right' track with God. How would you do that by yourself, without a church and without a leader? That's when you get into all sorts of trouble, making excuses for yourself and for your sinful lifestyle because you have no one to check you.
See also: We are Family
and Why I Hate Religion, But Love Jesus by Marc Barnes
Edit: If you can't make your point without calling names, then I'll delete your comments. Sorry. For the person who also made another comment responding to the name-calling, I didn't realize that your comment would also be deleted, and I can't remember who left it. My apologies.
If you believe that I can't possibly know why people leave the church, you're wrong. I'll leave it at that. If you don't want to believe that Christ left us a church - filled with people, sinful though they may be - that's your choice. You'd be wrong, but that's your choice.