Probably since they don't want to give away the million and it creates more of a challenge. Notice how a few people are close now, with the closest being 24. If the game never ended then they could just wait until three obvious picks came up so they would have a better shot. Instead since there is only three days remaining they might have to pick games they don't feel confident in to increase their streak. I'm kind of glad they're resetting it, since my record is horrible.