Manipulation through fear, mainly.

It’s definitely declining in the developed world.

It's all due to their ability to provide a sense of belonging, moral guidance, and a connection to something greater than ourselves, IMO. While belief may have fluctuated over the years, religion still plays a significant role in many people's lives. I've found a blog where you can find a lot of thoughts on that. Here it is whenyouneedgod.com. I'd love to hear your thoughts on the topic and discuss how traditional religions continue to shape our lives.