Tip Creep
The tablet swivels. Three buttons: 20%, 25%, 30%. The line behind you waits. That screen was set up by the company that sells it and the business that bought it, not by the person handing you a coffee. Tip Creep is a friend in your pocket for that moment.
Decide once, calmly, what you tip and where. Keep the money where a screen is the only thing asking, tip for real where you sat down or someone brought it to your door, and watch what you keep grow into a book you want to read.
No account. No analytics. No location. Everything stays on your iPhone.