Sorry, by ”this thing”, do you mean an iPhone? That it looks less professional to use a phone than a dedicated card reader? I can see it, I was just genuinely a little thrown by the wording.
Sorry yeah. I don’t know why I shouldn’t trust tapping on someone’s iPhone but it doesn’t scream “professional shop” in the same way that those card readers do. Even though those card readers are very cheap and ostensibly work the same, they just feel more “professional”.