The main reason is that it’s a game and that’s one of the rules! The reason there a time limit to enter points is that this is a game about behavior, awareness, and consistency. We have discovered that the more structure the game creates, the more consistently players stay aware in their daily life and the more they stay engaged in the game for the entire eight weeks.
It is very important to understand that this game is NOT a log. The entries that you make into the site reflect the rules of the site. Those include both the guidelines for the different categories and the way you interact with the game site, i.e. daily.
It is also valuable to recognize that this game is NOT about getting a perfect score. Your score will represent how you interact with your health and fitness. If you can find ways to follow the rules of the game the way they are written, you will find yourself having a different daily relationship with your health and fitness.