[mistercool]

Assuming it's true that they receive a similar proportion of cash tips from cash purchases as digital tips from digital transactions, I wonder if the variability is substantially greater for cash tips. It seems reasonable to assume pre-selected tip amounts on Square would decrease variability, while cash purchases probably opt for (no tip, resulting coins from change, or bigger bills). The five or ten bill tips mentioned in the article seem awfully high for a coffee purchase... perhaps older, wealthier customers tend to pay cash and tip in bigger bills.

[PebblesRox]

With cash it's more convenient to tip based on the bills you have available vs with a fixed percentage. Maybe some regulars will give a large cash tip some days and a small or no tip on other days, with the idea that it'll even out in the end.