The bigger issue is that the "best case" is more brought by luck than anything. I've lived plenty of places where walking that mile wasn't actually feasible. No sidewalks, for example. Work that expects employees to arrive to work clean and dry, no matter the weather. Work that provides little space to store winter gear. Sometimes, the drive is seriously shorter: You might be driving a mile, but they don't allow walking on those roads, so the walk is a mile and a half.
The social issues are important things to consider depending on where you live, as they might make it nearly impossible to walk without police harassment. Especially at 2am.
On the other hand, he keeps fit, enjoys walking recreationally and happily walks for miles when hiking, golfing, or fishing. But he'll drive his car as close as possible to the start of the trail first.
I am guilty of driving just to travel a mile, on occasion. When you do physical labor, have to carry your own tools, go to work before sunrise, and may not be done until well after midnight, it's really nice to know that when you get off shift at 3am you'll be able to hit the pillow 10 minutes later.
The bus sounds like nice solution, but it's more expensive ... and it shuts down entirely for the 4 hours that I'd need it most (1am-5am).
BTW, that's one of the major problems with public transit around Seattle. Rent is terrible, traffic is terrible, parking is terrible, and it's easy to say "so just take the bus", but we don't run the bus at hours when a lot of blue-collar workers need it.
The choice seems obvious to me.
So unless you're travelling somewhere afterwards, where's the upside?
Eg a math major can transfer to just about any engineering field with little cost, but its harder to go from say CS to a math major. Philosophy might apply to anything, while art history is quite limited in application elsewhere.
In the same fashion, you should not ask “unless you’re travelling elsewhere”, but rather, “unless you’re planning not to travel elsewhere”; the car gives you both options. You’ve essentially not made a decision regarding travel. Walking otoh does make a decision on the matter (at 15 minutes extra, outside lunch is less appealing; at 20-30, its likely unviable).
Thus, in this particular regard, driving needs no justification, but walking does.
Personally. Driving is stressful and uncertain (doubly so in cities with a lot of traffic), while walking is nice and relaxing.
Would you drive, just to travel a mile? Barely seems worth it in the best case. That's without getting into the environmental and social issues.