There are some circumstances you may want to make certain preparations based on the possibility that one candidate or the other may win, and polling trends can help you determine what sort of plans and preparation you should be making.
One example that comes to my mind is that prior to Trump getting elected, my wife was concerned that a trump presidency could lead to Republicans killing Roe V Wade and/or making it more difficult to access birth control, and so she opted to get a longer-lasting IUD prior to the election.