I knew a girl a long time ago, came from a small village and was quite religious. I'm not in any way shape or form. So I asked her about it and why she bothered and her answer was a very honest one. It was just something that brought the community together. They didn't care about converting others. They just didn't care if other people believed or not. They didn't care about gay people or any of that other stuff that gets so many religious peoples knickers in a twist. It was about them and their faith bringing them together. That aspect of religion I can understand. Like you, I think these things can be done without religion, but feck it, they're not harming anyone so if it works from them then, cool.
I've always said that people like being in groups, feeling a part of something bigger and having other people around you who think similarly, and that can manifest in many ways, good and bad (gangs, political groups, even sports teams - obviously all very different but all unite people with 'a greater cause' at the centre). I fully believe the church falls in to this.
Often hatred brings people together too, and that's when you get the fecked up religious groups, or other groups that don't base it on religion.