The only reason to phrase your question the way you did is to increase the FUD surrounding car services like Uber and Lyft. The same question could be asked of any person in any profession.
Regardless, the answer to your question is the first result when you search Google for "Uber liability coverage":
> Uber holds a commercial insurance policy with $1 million of coverage per incident. Drivers’ liability to third parties is covered from the moment a driver accepts a trip to its conclusion. This policy is expressly primary to any personal auto coverage (However it will not take precedence over any commercial auto insurance for the vehicle). We have provided a $1 million liability policy since commencing ridesharing in early 2013.