Maybe less cynical answer: maybe because Uber states that they provide insurance for drivers and riders and that’s why?

https://www.uber.com/us/en/safety/#

There’s auto insurance to help protect you Leading auto insurance providers help protect riders and drivers on the Uber app. Uber maintains commercial auto insurance in case of a covered accident, including at least $1 million in liability insurance on behalf of drivers and delivery people once a ride is accepted.