I would personally hate to have a ticket book system.
~There would still be an admission fee, plus the cost of parking, plus the cost of tickets, it could wind up costing you more than a single day ticket
~If they used actual tickets, they would have to add in the cost of printing, distributing, and collecting the tickets
~If they used a card or wristband system how would you keep track of what "tickets" you have left if you didn't purchase a ticket for everything
~Rides with cheaper tickets would become more crowded and rides with expensive tickets would become deserted
~It would be a cheap atmosphere, like going to the fair, rather than a vacation like going to Disneyland