Why? As much as we know about the world there's still a ton that is unknown and stuff science can't explain. Leaves plenty of room for faith/religion.
1) It is okay to say "I don't know" We don't have to make up fantasies...
2) And making up fantasies is good and entertaining, the problem with religion is that the people who follow them start equating fantasy with truth...If you want to believe that Jesus or whatever created the world in 6 days, even in the absence of scientific proof, that's fine, indulge in your delusion, but don't pass it off as the "truth"...
I think that is the biggest problem non-religious people have with religious people...
3) When Ben Carson states that he believes that god literally created the world in 6 days, then he is placing himself in the same category as Trekkies who believe that Kligons actually exist...
I don't know about a president who holds childlike ideologies in this day and age...