Big box grocery is a big part of the problem. We've got a relative abundance of grocery stores here - in US terms, but that means a 2-5 mile interval between then, and who is going to walk several miles carrying groceries? It doesn't help when competing groceries open directly across the street from each other, but even fixing that and making distribution of the current stores more even, there would still be a lot of the population 2+ miles to the nearest store, in our relatively high density suburban "core". Get that down to a maximum of 1km from every home to the nearest grocery and you're starting to have a walkable / bikeable solution for food.

As for bikes, we also have near-zero practical support for biking to get your groceries - starting to get something calling itself bike lanes, but they're not terribly safe looking, and then you get to the store and you're extremely lucky if there's even a rack provided to lock the bike to - the racks that do exist seem to be in direct conflict with pedestrian use of the sidewalks.