Dave’s travelling to and from work. He’s not sure what time he’ll finish and whether it’ll be peak or off-peak. The only ‘safe’ option is to buy a peak, but if he works late he’ll end up overpaying, as an off-peak would have been cheaper.
With Hindsight, he just comes home when it suits him and we’ll flip him from the morning’s single to a peak or off-peak return as needed. He doesn’t need to think about it and he’ll never overpay. If he could have saved money, he will with Hindsight.