Why do creationists believe the world was created 6k years ago?

This is what I don't understand. If you follow a literal interpretation of the bible, why do you not believe the world was created 6000 years ago in a week long creation event?
Is it that you have no argument against some of the evidence that geology provides that contradicts such a short time-frame, such as the sheer depth and number of strata that have been laid down; that some rock formations take long times to form, like limestone; or even radiometric dating methods all giving a similar ~4 billion year age to the earth? How then do you, for example, account for the fossils incorporated into these strata? Why do you find it necessary to shoehorn long periods of time into the story rather than basing your interpretation on what is actually written?