Likely they see self-driving as a complement to their core business of vehicle-passenger matching rather than something they hope to profit from directly in a meaningful manner, in which case "commoditize your complement" applies.
"A classic pattern in technology economics, identified by Joel Spolsky, is layers of the stack attempting to become monopolies while turning other layers into perfectly-competitive markets which are commoditized, in order to harvest most of the consumer surplus."
"A classic pattern in technology economics, identified by Joel Spolsky, is layers of the stack attempting to become monopolies while turning other layers into perfectly-competitive markets which are commoditized, in order to harvest most of the consumer surplus."
https://www.gwern.net/Complement