I think they only did it one year because it lost money. I remember you had to pick a date and buy your ticket in advance. I guess they did this so that they would know how many people to schedule to work by how many tickets were sold. People did not like this system because if it was raining or some other kind of bad weather, they could not get a rain check or trade the tickets in for another day. With the current way they sell tickets, where you can buy them at the gate or get them off line on the day that you are going, people might skip a rainy night but come on another night. With Paramount you were locked into that date you purchased and if it was too wet and miserable to go, especially for your kids, you were just out that money. Paramount was afraid of losing money on a dead night where as Cedar Fair knows that if they don't get you this weekend then they will most likely catch you next weekend. This works for the park and it makes the guest happy to have options. Plus Cedar Fair allows season pass holders to use their passes where Paramount made pass holders pay for the event. Although Cedar Fair is not making any more money for pass holders to get in, the pass holder is still buying t-shirts and funnel cakes and that is just extra monies that the park might not otherwise make.
This is just my best guess though. I don't claim to know Kings Island's business and I could be way off.