Well there are 10 tracks. I just want to give people enough time to hunt all the tracks in case they wanted to, to better their odds at winning.
The reason I put the date for the driving contest a little later is so that I didn't have to deal with the results for the driving contest at the same time as the judging for the building and screenshot contest were starting.
I also think it would be unfair to move up the date since it was already announced. I agree that a week or two is probably more than enough time for the driving contest, but it certainly won't hurt anything to let it go a little bit longer.