We don't usually fine people or send them to prison for mistakes, especially when driving cars. Insurance companies figure this out between each other.
If a self-driving car gets into an accident that kills a pedestrian or other driver, someone's going to have to take responsibility for that.
In the US, killing someone with your car while being drunk and driving twice the speed limit gets you 10 days in jail: "10 Days for Bobby Cann’s Killer, a Repeat Drunk Driver, Is an Insult" (https://chi.streetsblog.org/2017/01/27/10-day-sentence-for-b...)
Bad drivers absolutely get fines and jail time for speeding, DUIs, etc.