I really think that the main reason people believe in god is because it provides them with a way to understand the universe that puts everyone on an even playing field and doesn't make them feel stupid. Most people don't have a good grasp of even the basic scientific concepts that help explain the world around us and they are intimidated by science. Its uncomfortable and belittling to accept that there is an explanation out there that others can understand but which you can't.
Science is also about uncertainty. Its the drive to understand what we don't already know and that uncertainty makes people comfortable. In the recent debate between Bill Nye and Ken Ham when asked about where the first atoms came from Nye said that is still a mystery and its the beauty of science that we can investigate and look for answers to these questions. Ham retorted that in case Bill wasn't aware there is actually a book with the answers to all of those questions at which point the stacked audience cheered and laughed in approval.
Denying a scientific explanation for the origin of the universe and for human beings and insisting that there is a god is a way of saying there is an easy ready made explanation that we can all understand and in fact those scientists who think they are so smart are really the ones who are in the dark. Religion is the great equalizer.
Obviously there are many reasons people believe in god but having an easy to understand ( on the surface at least) explanation for the universe and why we are here is a huge part of it.
Reading a genesis story of beginning from the pre-history Rig Vega. Ancient man seemed to have a lot of the same problems. The way they explained it was.
At first there was the universe. How it was create or came to be, man may never know.
Then earth was made from matter.
Then energy was formed.
Then man was created from energy and matter.
Then god was created.
Note, I left out a lot. But the point being is that back thousands of years ago they were thinking about how the universe was created. Note, that they had god coming after man. I should note that god was not a deity at that time, god was the collection of man's knowledge.