Uber's appeal to me has always been not needing to worry about cash and tips. I've only once tipped a driver, when I needed to move two boxes across town and the driver kindly got out and helped me bring them up the driveway. I too would feel like I'm being extorted in the presence of such a sign, as it signals no tip would result in a bad rating.

Heck, if people continue to tip for the usual service that may become the norm anyways -- I'd like to thank them in advance for ruining what was a super convenient, stressless, tipless alternative to the despised American taxi cabs.