Did you notice the people happily saying that you could see the produce?
People don't trust some things without being able to see them, and food is one of them. Being able to recognise that a particular item is the one you like makes them happier.
Once they've used it a couple of times they'll be re-ordering without bothering with the scanning, but to bring in first-time buyers, this is very smart.
Another thing that I'm sure weighed in positively (at least subconciously) was seeing others do the same. On a singular device, the experience is very individual, could be experimental, and feels like shopping in a box: a tiny flat one, at that. Out in the public alongside others breeds a sense of community approval and helps reinforce the legitimacy of the method, especially as it is somewhat close to the original grocery shopping experience.
People don't trust some things without being able to see them, and food is one of them. Being able to recognise that a particular item is the one you like makes them happier.
Once they've used it a couple of times they'll be re-ordering without bothering with the scanning, but to bring in first-time buyers, this is very smart.