Given the "unpredictable behavior" of the target demographic, the wages and training of staff and basic economics - it's amazing there aren't more tragedies at amusement parks.
Six Flags, at least, made you take certification tests. You had to pass one to be an attendant, another to operate (work the control panel), and a third to train others.
Depending on the ride, the operator and trainer tests could be pretty exhaustive. They also wouldn't let you take the operator test until you were ready -- either working the ride a few weeks, or clearly knew what you were doing because you'd worked other rides -- and had been instructed and cleared by a trainer.
The attendant tests, though, were pretty simple. Some rides, they could get you to pass those with 15 minutes of training and 15 minutes to take the test. The hardest part for some tests was learning where all the fire extinguishers are.
A couple of times, someone was certified as an attendant just to cover a lunch break or two.
I got an attendant certification for one coaster just for the hell of it. My friends worked it and talked so much about it when we hung out that I knew most of the basics before I was formally trained. Only time I ever used it was to cover a bathroom break.
We were all coaster geeks and took it pretty seriously, though. It was fun to have that knowledge and apply it. It was 30 years ago. Who knows how the motivations of the current generation work?