I do not know what you are employed as but, if in your workplace, you make a mistake, others are very annoyed but no one is hurt - would you accept having your employment terminated as a fair sanction?
I think in all lines of work you have things that can be done even accidentally that fall under a zero tolerance policy. I was speaking with a dustcart driver a few days ago that had 6 month suspension for collecting a black bin bag from the roadside as it was seen to be private waste and not the council bins they had been told to collect. Honest mistake but they have a policy so people can't get cash in hand for other rubbish. I can think of dozens of jobs where data misuse would get you fired instantly(my own included). Any jobs involving cash handling and clear instructions on how/when it should be handled.
With driving jobs they do have more training than other drivers and are held to higher standards. For many coaches/buses/trucks the driver would have had not only more training and expectation but also sensors and warnings in the cab as they got closer to a rider, it's a very conscious choice to ignore all them things.
It's also the wider impact of incidents, many companies just don't want drivers who take those risks as they have come to understand that when they do eventually kill someone from habitually bad driving the impact will be felt company wide as they lose contracts and gain a poor/unsafe reputation.
Often with this stuff the mistake the driver is saying sorry for is getting caught and not how they had been driving or attitude they have towards the road. Unfortunately very few and far between where it's a learning point for a driver.
edit - ps don't send people on safer urban driving as a punitive measure it just gives the instructors a really hard day