The driver rating system really puts drivers in a tough spot. When someone asks them to make an illegal maneuver, they can either say no and risk damaging their driver rating, or say yes and risk a ticket.
Taxis don't have this issue because you can't rate the driver if they say no.
Given a random sample of cars in downtown SF, what percentage of them are Uber/Lyft drivers? Is it more than two-thirds? Without that information, this number is meaningless.