Bill's nailed it. It's all about TIME.

Creationists don't have enough time in their sequence of events since creation to squeeze everything in: the development of so many diverse and disparate life forms, the laying down of sediment, the action of plate tectonics, the cooling of the earth, chemistry, the formation of the oceans, the time it takes for light to reach us from other stars, the formation of the moon, the existence of any number of observable cosmic events and objects.

Deep time is a very difficult concept to grasp, and that's just the geological timescale. By the time you're talking about the cosmic timescale even a relative demonstration becomes meaningless as the time distances are so huge. I'm not sure any of us are capable of grasping these ages - we live for a paltry three score years and ten and have a very constricted concept of time.

Much easier (and lazier) to chalk it all up to god and then not have to think too hard about anything.