We don't. 42K people are killed in the US every year in automobile accidents. Yet humans are allowed to keep driving and killing people despite their massive flaws.
Individual humans have their license revoked and sometimes even face manslaughter charges if they cause too much death on the road. FSD is like one mind in control of an entire fleet. It's mistakes are amplified relative to a lone human
And yet, the average driver kills 0 people. It’s in the far margins where deaths occur - a fraction of a fraction of a percent.
This is in comparison to the arguably singular entity “Tesla Autopilot” which has already killed several.