I debate more to refine my understanding and to understand why someone else has theirs. That aside it is using two different ideas that have different burdens of proof. Science is a series of theories that try and provide a best fit to the data and remains open to be debated and modified as better techiques, data and understanding come about. Creationism is a literal translation of two different (conflicting) allegorical tales which does not require any proof but is a faith based execise.

Creationist "Evolution is only a theory."
Scientist "Damn straight it is, just like gravity is just a theory."