https://www1.nyc.gov/site/planning/zoning/zoning-maps.page
They appear to have each section of the map available as a PDF. I guess everyone just does it a little different. I'd expect NYC to be closer to Boston though since they're from the same era and both have limited area to spread and have a lot of grandfathered in buildings.
I'm a bit surprised DC is so segmented by land use, though I suppose it's a more recent city it's not as if 200 years is chump change. It seems like the zones are created and existing stuff gets exceptions carved out, and if they get torn down then they lose those exceptions and become the default type. So if buildings get destroyed quickly or if there's a lot of space for new construction I'd expect more simple separations between land use types.
http://maps.dcoz.dc.gov/zr16/#l=12&x=-8575451.094054567&y=47...
All the yellows and browns are residential zoned. And almost no mixed-use zoning. This makes your experience sound as if by design, not as nature would do it.
Well, looks like that regulation isn't great for stores. Here's the exceptions to residential units in the residential apartment zones:
https://dcregs.dc.gov/Common/DCMR/RuleList.aspx?DownloadFile...
Huh. 420.1.c explicitly bans corner stores. 420.1.g kind of looks like you can do a store under the apartment at least. This zoning map really doesn't look friendly to foot traffic.
My experience was as the OP, grocery stores I haven't even bothered to try yet within a 10 minute walk. This is the zoning map of Somerville.
http://3pb8cv933tuz26rfz3u13x17-wpengine.netdna-ssl.com/wp-c...
It looks totally different, granted the scale is much different.