The implication is that 20% the widely accepted minimum "good tip" rate, and consistently tipping 15% is consistently being cheap. Especially when you're a tech worker FFS.

Let's break out of our echo chamber a bit. In the US, tipping isn't "paying more than required," it's basic manners. You can argue until you're blue in the face about how businesses are to blame, but the vast majority of society, who have no big beef with tipping culture, will find you cheap rather than discerning.