How is that a worse experience? I don’t have to mess around the bill to add a tip, I just punch it into the machine and then tap my card or phone. It also makes it super easy to split a bill if you are in a group.
They have to carry it around. They leave it in the back, on the counter, whatever and have to go get it. They want you to hurry, they only have one of them, they have a lot of customers. You are interrupted to pay at their convenience, not when it's convenient for you. You have to fool with some gadget with a terrible interface when you'd rather be chatting with your sweetie. It's more awkward to leave a tip in cash (you tip zero on the device while they're watching).
It was a terrible idea.