In parimutual betting you are not betting against the house, you are betting against other people but obviously when you wager early with a lot higher amount odds (for example who will be the next president had like 10+ candidates and later only 2 so odds changed a lot) I assume it would have been a bit difficult to calculate without time weight. Think about it, you gamble so early that your bet looks like x35.00 odds but later on when it gets closer it is 1.8, how are you going to claculate that without the weight? Which means the earlier you wager (or maybe later, if the odd grows bigger later on) you are going to have better result but not a HUGE margin, where it ends up before the bet closed is the most important odd, after that you get that multiplier depending on when you gambled.