Theme park owners don't want to take chances and most of these actions are VERY conservative. Consider SeasWorld and the "Journey to Atlantis in San Diego". Any event that requires an e-stop requires an evac. Lets say a kid gets off the ride on the transfer track ahead of dispatch(happens often), obviously an e-stop should be made. But even if the kid was easily retreaved, ALL of the passangers anywhere on the ride must be manually removed. The process though is very safe and is very well trained, practiced and tested. BUT it is a royal pain.
The ride that I had the most fun and laughed the hardest at being stuck was Kongfrontation at USF. Our vehicle would not stop for us to disembark. We made the loop throughout the ride eight times before they were able to get it working properly. Our "guide" went ahead and did the ride's script each time. We were all laughing so hard, because eventually he would sound more and more bored. By the seventh time, his dull voice would say, "Oh no. He is going to hit us. Watch out." We all left knowing the lines so well, that we could have easily been hired. After all these years, I still remember some of my favorite parts, "What's this? It looks like a war zone!"
About 10 years ago my family and I, where passing in front of the Hulk (before it was dirty), we rode it earlier that day, but wanted a second ride. It was Summer (July to be exact) Islands was PACKED but we decided to go in, so we stood outside in the queue really near the building entrance. Then all of the sudden a voice says that they were having some problems, and that guest could wait or come back later. So we decided to wait it out... We waited people kept leaving and we move forward and a little more forward but the "damn" music and videos were left playing. So we moved a few feet stay there for about 10 minutes of the same, then move again to ten more minutes of the same music/images etc. Until finally we made it to the loading area after waiting about 45 minutes with that annoying song/video of the Hulk transforming and fighting the ARMY and a damn tank!!
I still, to this day (10 years later) remember that damn video!! So I agreed turning the music/animations off is a great idea...
That's TONS of fun :P