The disruptive effects still happen even if we don't get to 100%.

For example, a train of self driving trucks can be led by 1 in the front. Yes, I know, REAL trains exist, but they don't go everywhere. A train of self driving trucks could save a lot of money.

If self driving Taxis don't work in the rain, then Uber can just NOT drive them when it is raining! For example, Maybe the penetration rate will be very low in Seattle, but very high in Texas. Disrupting 20% of the Taxi market by eliminating drivers is still a very big deal.