I recently ordered take-out pizza from a major chain using their app. Their default tip options (for take-out, now, not delivery) bottom out at 20%. In big red boxes: 20%, 25%, and 30% -- and then an understated "Custom" wording at the bottom.
Once I arrived at the place -- having processed the payment and tip through the app -- I had to sign a credit card receipt for some reason. On THAT in-store receipt ... there was ANOTHER tip line. I wrote in "on card" and added $0.00. Already tipped on the app, so no.