The point isn’t to force people to walk to get groceries. Rather, the point is that many cities have made it essentially impossible to get groceries on foot, even for those who want to. For example, Euclidean zoning in the US and Canada makes it literally illegal to build grocery stores (or any other commercial spaces) in residential areas, meaning grocery stores will be way too far from where most people live to be practical to walk to. Similarly, parking minimums mandate each store have a large, arbitrary amount of parking out front, even if the store owner doesn’t think they need anywhere that much parking. The effect of this is to needlessly spread out cities, yet again making it harder for people to walk to the store if they wish.

If you live in a place where it’s practical, where local laws don’t literally forbid it, walking to the grocery store in January genuinely isn’t bad in the slightest. I live in Montreal, which gets pretty frickin cold in January, and yet everybody and their grandmas walk to the grocery store in my neighborhood. Why? It’s a reasonably dense, walkable neighborhood with several grocery stores within a 5- to 10-minute walk of tons of people. I myself live a 5-minute walk from two grocery stores. For me, scraping ice and snow off a car just to get groceries would be 1000x more annoying than just popping on over to the store on foot.

You will spend more time warming up your car, than walking two minutes for your groceries. Why waste time?