Because the God image they have fashioned is recognizable and identifiable. A God that can create the Earth and animals and stuff in a few days is easy to comprehend and deal with. Like Star Trek's "Q" without the attitude.
A God that can create an entire complex process that proceeds forward requiring millions (or billions) of years? That is a God that is too complex to deal with. Create a Universe with rules that mankind may never understand? Too humbling. Better that giraffes, chimps, starlings and ostriches all just come into existence *poof*. Much more manageable and you can actually get a simple mind around it.
It is humbling that God created a process (Evolution) that ended up with such a beautifully complex thing such as a human being. It is sad that CRIDers put handcuffs on the ability of The Almighty.