One of the strongest scientific theories to date, even stronger than the theory of Gravity and there are still people out there that reject it. Why? I can't get my head around it, I can show you facts, papers, journals, text books, fossils, just evidence piled on-top of evidence and it's.
Nope Science is lying to us or my religious ancient book says different so it must be wrong.
Is it the fact that they don't understand it or that they don't want to understand it? It's gotten to the point now that even YEC have had to accept evolution to a certain degree and decided to rewrite the definition of Macro Evolution just to say it doesn't exist. Nothing and I mean nothing in biology that we've learned in the last 100 years makes sense without evolution as a whole NOTHING! The Theory of Evolution is as important to biology as the Theory of Relativity is to physics.
Food for thought.
Edit: Here if you're still confused about evolution