They are new names for existing crimes that were invented to lessen the penalties.
Additionally, enforcement is extremely weak, and even with these lesser penalties, police will do everything they can to avoid dealing them out, even when they apply.
This is by design and it wouldn't make sense otherwise. It would be crazy if 50 legal jurisdictions just happened to all reach the same wrong conclusion. Driving a car non-negligently carries an inherent risk that you will kill someone and this risk is borne by all drivers. And we've decided that this risk is acceptable and legal to take on. You are explicitly allowed to do a thing that has a non-zero chance of killing someone else.
It would be ridiculous if we locked up the people who happened to kill others while not driving particularly dangerously. Justice is not being served by locking up the unfortunate unlucky sods while everyone else is engaging in the exact same risky behavior. It's why cops are unlikely to go after someone who say killed someone while speeding a not crazy amount; the thousands of drivers that go by every other day are doing the same thing. But they will throw the book at the statistical outliers of dangerous driving.
Don’t forget that the bar for negligence that also allows random distracted soccer moms, burned out and exhausted workers, and the 25% percentile of the bell curve to drive isn’t very high.
But if those folks couldn’t drive in the US with the way things are currently setup socioeconomically, everyone would have a huge problem.
And it usually isn’t that big of a deal - or at least emotionally doesn’t feel like an unreasonable risk, which is all society cares about.
