Because, as an earlier post said, evolution is strictly speaking, is scientific law.
It's like a chemist questioning the existence of atoms and molecules. There's nothing wrong with a chemist questioning some detail of ill understood molectular structure of some complex compound. But to reject the entire basis of the science of chemistry? That's just beyond the pale.
If creationists or ID people want to dig into the details of biology and start to change some thinking on the details, and evenutually prove the earth was snapped into creation by God's fingers from nothing. Then go at the details. There's plenty of questions there.
Reminds me of Hitlerism ... sieg heil --- evolution !