I live in Seattle. Many neighborhoods are very walkable. I can and do walk to grocery stores all the time. No, I don't know the cashiers personally. I also have to wait in long lines quite often.
When I lived in New York, one of the most walkable cities on Earth, it was even worse: long lines and anonymous, interchangeable cashiers.
I grew up in a small town where everyone drove to the grocery store, and that's the only time in my life where people knew their cashiers and genuinely cared about their lives.
Effectively, you still lived in a village. One neighborhood in Cincinnati functioned like a village for me in the early 2000's.Many neighborhoods in Barcelona function that way.
When I lived in New York, one of the most walkable cities on Earth, it was even worse: long lines and anonymous, interchangeable cashiers.
I'm not, as you imagine, touting walk-ability as a panacea. My point is that it's the societal structure that gives the humanity perceived by the Barcelonan commenter, not the checkout jobs per se.
I know all the people who work in these supermarkets.
The significant bit is that the walk-ability indicated in the 1st sentence enables the community indicated in the last sentence. I know there was one neighborhood in Cincinnati in the early 2000's, where you could walk to the grocery store, walk to the hair stylist, walk to the library, walk to the bank branch, and have a friend shout from their balcony to invite you up for dinner. Enable people to interact with their world on a village-scale, and you will have village-like interactions. However, if you turn people into paranoid-other-ignoring drones and cargo in metal capsules, then you have dystopian sci-fi city interactions. (This is a spectrum, not a binary bit, of course.)