The question is, why would anyone lean towards the idea that the earth was much older than 6,000 years? If it is because of what science and the media say, the scientists tell us themselves in their papers that they are not sure. It is the media and the universities that have made up the whole idea of millions or billions of years.
The evidence suggests the Earth is much older than 6,000 years... that's why... it's not someones opinion, it's based on facts and evidence
On the subject of certainty... you claim to know for certain the Earth is 6,000 years old, based on no evidence at all...
Scientists rarely claim certainty of anything... Scientists present the evidence, and their opinion on what the evidence suggests... and all the evidence suggests an Earth that is billions of years old, not thousands... the evidence for such is overwhelming... you have to intentionally blind yourself from the facts to believe the Earth is only 6,000 years old... period... end of debate
The person who claims to be certain, is certainly a liar *cough* BADlogic *cough*