Even if you live in the urban core of a dense city like Boston, NY, or Paris, you can't realistically walk most places you would want to go.
The parent was specifically talking about walking rather than taking public transit. Boston has a particularly dense core and yes, so long as you confine yourself to the original Boston core (North End, Beacon Hill, Financial District, maybe add the Back Bay), you don't really need to use public transit. But I'm probably not going to walk from there to Harvard Square in Cambridge, Symphony Hall, or even the Seaport on a regular basis although I could.
Even in normal times, 99% of my transit usage is for leisure rather than necessity.
https://www.smartcitylab.com/blog/governance-finance/paris-1...