Where do you want to go? Living in a city center right now. It's hard for me to find a thing I DON'T have in a radius of 4km, which is a reasonable walking distance.
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.
I'm not familiar with Boston. But I think NY and Paris are actually too big for everything to be walkable. In smaller cities that's definitely possible. I used to live in Bristol, UK (pop. ~500k) and if you lived centrally then you get pretty much anywhere within 30 minutes of walking.
ideally there would be no need to get to the bus stop - if most of your needs could be satisfied within walking distance.