I can walk to the nearest shop fill a small rucksack/daysack with the day's shopping and be back home in 45 minutes without hurrying.
When I used to buy groceries daily on foot, it took me about 5 extra steps, one way, to get to the store from the sidewalk that I was already traversing from the bus stop that was 150m from my apartment... and then I carried them 100m to said apartment. That is the density that most people can accept when they think about "walkable"... These days I pick up a week's worth of groceries (impossible to carry, and I say is as a backpacker) on my way from the gym, or occasionally in a separate trip that takes the same 25 minutes round-trip for travel, except I do it once a week, or could do it even more rarely. And if you drive, it doesn't really matter if the store is 2-3km away on the street (which it is), or if it was 10-25km away on a highway.
Again, my point is, for most people, in most circumstances, 1km is a borderline unreasonable walk, and 2km is absolutely unreasonable and not "walkable" in any way. Sure, for some people in very special circumstances (and climates, or times of year) it might work out, but that is not a good basis for policy.
Also frankly it's just an inferior quality of life when your walk is to the grocery store thru dense burbs... I happen to have 2 large-ish parks nearby so I walk there, but not every day and in any case neither is on the way to any grocery store. I would never just walk around the neighborhood - instead, if both were 1km away, I'd drive to a park or a hike if I had to... then drive to a grocery store.