In every episode where people are seen riding roller coasters in Dinoland, there are no safety harnesses in the cars. That means during a loop, the riders would fall out of the car and die!
Even without a safety harness you would not fall out of a roller coaster unless it was going slow. It's like if you had a bucket of water and you grabbed it by the handle and swung it in a loop all the water would not fall out. In fact, none of the water would fall out. It all has to do with force.
It's more time efficient for the artists not to go into that much detail. It takes thousands of animation cels to make up a cartoon, think how long it would take to include that much detail.