Very true observation. I've tipped quite a few times at coffee and similar kinds of shops, on the tablet when they flip it around towards you, and I've never received any acknowledgement about it. I'm not sure if they are checking ungratefully or just not checking, but I've stopped tipping in those situations.
On the other hand, I don't think I've ever received exceptional service in that situation either. I'm not sure what that would even look like. Beyond some eye contact and a friendly tone, what is the tip supposed to incentivize?
I do it because coffee shop employees get paid poorly, and get little respect or status from the job. That's not fair!
I second-guess it not from losing money, but by tipping, I may be incentivizing this low wage. I.e. I don't like the idea of tipping, but it's an easy way to contribute back to people who are getting hosed by our system.
On the other hand, I don't think I've ever received exceptional service in that situation either. I'm not sure what that would even look like. Beyond some eye contact and a friendly tone, what is the tip supposed to incentivize?