You tie up less money. If you only have $100 in your account, but want to play a couple of games and really like the second game. Problem is the first game goes into OT and it is tying up your funds. It would work like this:
first game starts at 8:00 - bet $50 on Miami vs Chicago. If it wins you have $150
second bet starts at 10:00 bet $100 on Phoenix. It will only bet the $100 if the first bet wins.
If the first bet loses, then the second bet is cancelled.