I suspect decreasing tips also has a lot to do with tip exhaustion, I think it's becoming increasingly acceptable (at least in my circles) to hit the "custom" option and put in a smaller-that-suggested tip (or even nothing at all).
For counter service, not table.
I used to drink a fair bit, so at the end of a tab, I did not want to do arithmetic and would just put an “easy” number that looked good. This could often be upwards of 35%
But if you stick a touch screen in my face with even easier, one-two taps on a preselected amount, I’ll go with that.
Also I’ve accidentally no tipped a few times with them because I get frustrated with the incessant screens asking about receipts, emails, etc. that I just click past the tip screen.