Religion isn't just about evolution and how old the earth is, those are distractions from the big issues. All of the knowledge in the world won't help you deal with the questions, "Why am I here?", "What is my purpose? What is the point of it all?", "Do we just die and disappear?" Knowing all the science in the world won't make you feel at peace with these questions.

We are emotional creatures who are sadly aware of our mortality. Many need a parental figure to keep us in line, "God is watching", and a companion for loneliness and hopelessness, "Jesus loves you" when no one else will or can help. It can feel like you have some protection against things overwise out of your control (disasters, wars, sudden deaths, accidents, illness, etc). Many people like the structure it brings their life and the comradery from being part of a like-minded group. Some join the military for this, some go into orthodox religions thick with rules and traditions, like Hassidic Jews. It can lead to a strong tribalism too, same with politics, where you instinctively distrust those who believe differently but feel you can trust those who do because you feel you understand what they feel and think.