Basically, because a fundamentalist interpretation of the Bible contradicts evolution. You have a very different view of religion than a fundamentalist. To a fundamentalist, the Bible is THE truth. Anything that could possibly contradict it is wrong. I think it comes down to the concept of biblical infallibility and I can understand why someone would take such a view. If the Bible is not an accurate guide to verifiable events(things that happened in reality), than how can one say it is an accurate guide to anything? The only thing left for the Bible to guide would be subjective events that are simply in the mind of the believer. Those outside events provide validation for their belief.
The problem is that they then take the opposite approach of rationality. Instead of checking other evidence to see if Biblical events are true, they are checking the Bible before seeing if the other evidence can be true.
That and I think they want to believe humans are somehow super special creations of God fundamentally superior to all other species. It makes them feel special thinking that God created all these other species for the purpose of serving humans.