Arguablly different tariffs for different usage so if you have a lot of night time usage you might find its worth being on a tariff that rewards using power when there is less demand but in reality you make a good point. What about fixed price ones where you committ for a longer period to get a fixed rate - how do they work now ?
And lo-and-behold, all the cheaper tariffs will disappear and the only one left to "offer" will be the highest one. They're not daft these energy cartel people you know.