I mentioned elsewhere how people compartmentalize their beliefs, "playing" with them more than actually incorporating them into their lives. It's not that hard to find a religious person who claims we are in the "last days." Five bucks says he has a 401K going.

People answer surveys on this in the same way that they would answer a survey on their favorite color. Frankly, most people don't give a rip how old the planet is. While ignorance in this area is nothing to be proud of (any more than ignorance in any other area), you have to concede that it doesn't impact most normal lives in any way.

The hypothetical investment banker might reasonably point out that the age of the Earth really doesn't have much bearing on your financial decisions. Some people speculate that we are all part of a giant computer simulation. The proper response is, "so what really changes?"

Useless and stupid ideas have burdened the human race as long as it's been around. As one example, a large number of highly-educated people still believe that economic and political collectivism works, despite almost as much objective observational evidence against that then there is against creationism.