Tipping screens on touchscreen checkout/payment systems are an unfortunate tax on people who are afraid of social judgment or social conflict.

As tipping screens have become more common in retail/counter service through wider and wider usage of iPads as payment, and as suggested tipping amounts on the pre-selected options have increased, I have not started tipping any more at all than I ever did (20% on services where wait staff served our table but nothing for normal behind-a-counter transactions). I just learned to hunt down the zero percent button or the 'enter your own amount' button very quickly.