This question is probably best answered by discussing how the creation accounts in Genesis chapter 1 and 2 are interpreted. Believe it or not, there are actually a lot of differences of opinion within Evangelical circles.
People don't easily forget stories of powerful pastors taking money from vulnerable people who hope they can be cured, or that their prayers will be answered.
The decline of mainline church attendance in the U.S is a pretty well established fact. It only takes a simple Google or Yahoo search to confirm it. The hit to mainline churches far exceeds the very minimal decline of Evangelical churches.