I sympathize with the barista here, but mindset that customers need to cover 10 to 20% of his income is symptom of decades of brainwashing of employees and customers alike. In this case NPR is part of this brainwashing. I will not tip someone for doing their job. I will only tip when I feel it is needed based on the service provided.
Predictably with a margin taken out of it and reduced as much as possible.