You need training to guarantee correct reaction when things go wrong.
Here's an anecdote: I used to drive a car with a standard transmission in Los Angeles. In quite a few places, the parking spots have a "trench" in the front for drainage. So, you can place your car in reverse, release the brake and have your car roll forward quite a bit (the trench makes an even stronger downward slope on a hill that is already pointing downward) before the clutch engages. A bit surprising but nothing that weird for someone who drives a stick.
Now, have that sequence happen to someone driving a car with an automatic transmission. They shifted to reverse, the car is rolling forward more than they expect and is on a hill, they hit the gas to arrest the roll, the transmission engages and the car shoots in reverse. Pray that there isn't anything close behind them or they're going to run over a pedestrian, put their car through a wall, etc.
2) Because the majority of the people who had "uncontrolled acceleration" were old.
The vast majority of the cases were very likely driver error by older drivers who had incorrect habits ingrained. Toyota probably would have won the case if this was the only issue.
Alas, Toyota lost the case because their processes for safety were such a complete shitshow that they were going to get destroyed in court.