They said they are within walking distance, so I suggested wheels to avoid "walking like a mule".
A suburban grocery store is rarely much closer - even though there is typically houses behind them, there is a fence in between so you can't get there from those houses.
If the grocery store was on my way home from work that would be different: I can stop in to grab just enough for today's meal (and breakfast tomorrow). However on the way needs to be fairly strict. A suburban grocery store has the doors too far away from anyplace somebody would walk to be considered on the way - the additional to my trip is going to be annoying enough that I'm going to be getting more stuff when I do make that trip in turn meaning I won't use it.
The above assumes a pure walking trip. I used to take the bus to work. The bus stopped at a transfer point in front of a grocery store, the bus only ran every half an hour so I never got off for my shopping: it didn't work for a 5 minutes get what I need for today trip as the bus would be gone (5 minutes assumes I know exactly where the one thing I need is and that the line to checkout isn't long). I'd either have to waste 20 minutes, or I'd get so much stuff it can't fit on the bus - also there is risk of a long line making me miss the next bus.
Since we all need some exercise anyway, the days I go grocery shopping are days I don't need to explicitly choose to do some light cardio, because it's taken care of by the grocery shopping and any other errands.
But if this sounds too simple and we want to complicate things, then sure, we can complicate things and imagine scenarios in which it's impossible to do it. I am just saying for many people around the world, grocery shopping is something we do with a granny cart, and we don't need to be "loaded like mules".
It's just interesting to think how we end up in these situations and then society is what it is and individuals have limited power to change it on their own. (That said of course individuals also do have power and sometimes blaming society is just an excuse).