I love density, but, in my experience this is not true. London doesn't have a large competitive market of grocery stores. Neither does Boston or New York City.
Density means higher real estate prices, that means grocery store sizes go down, and the barrier to entry goes up. Yes you can get more small specialty shops (which is great!) but I've had times where I've had to go to 3 different large supermarkets to find some oddball item I needed, and density would make that even harder on me since stores would have a smaller variety of stock.
Of course the 2 largest grocery store chains in America are trying to merge, so very soon American cities won't have much competition either.
I'm not saying density isn't good, it is, and it makes lots of shopping easier, but certain types of (uniquely) American retail experiences fall apart when cities become more dense.
Heck Seattle already is dense enough that there is only 1 Costco within the city limits, the density of Costco's in the suburbs surrounding Seattle is actually quite high! Prior to living in the city proper, I was a 15 minute drive from two Costcos! Now I am a 30 minute drive from one Costco. Since I don't have the time to go that far on a frequent basis for groceries, I am paying more for food living in a city that has more grocery stores around me, than I was when I lived in the suburbs.
Multiple neighborhoods I lived in had walking access to Stop & Shop, Star Market, Trader Joe's, Whole Foods, Target, bfresh, cheap overstock/clearance stores, a farmers market, and other independent grocers, many catering to nationalities/ethnicities with large subcommunities in the area. Just a train or bus ride away I could go to Market Basket, Roche Brothers, Wegmans, a worker owned-co-op, and more farmers markets and independent grocers.
Costco was a longer train ride away, but accessible if you wanted something specifically from there. Delivery is more economical because of the shorter distances involved.
You can see this yourself by doing a map search.
In rural areas I've lived, one is common, sometimes zero within a fifteen minute drive. Suburban areas might have two or three regional supermarkets, plus Walmart, Target, Costco and/or Sam's, but always way fewer within the area covered by the same travel time.
Different parts of Boston is incredibly varied though, I shouldn't have made a general statement.
Here's a map of all of them: https://maps.walkingclub.org.uk/shops/
Alternative map: https://www.toptiplondon.com/food-drink/london-supermarkets-...
London does have larger stores, but it isn't like in America where the average grocery store is, well, huge.
(Obviously some chains such as Asda have larger stores!)
On the west coast at least, American grocery stores are either small like Trader Joe's (Aldi sized I believe), tiny local ethnic stores, or you start getting into larger and larger categories that start at "really damn big" and end up at "you can get lost here".
The "you can get lost here" sized stores typically have much cheaper prices, and families go there on weekends to buy essentials (meat, veggies) to stay on budget.
All in all I'm not saying it is a bad thing, having a higher density of grocery stores is nice, it means going to the grocery store isn't a dedicated trip, but those cheap huge discount stores are very nice to have around.
[1] I like to stay for awhile in the middle of cities so I can actually shop at local stores, cook some food myself, etc.
- Whole Foods
- Key Food
- 2-3 specialty grocers (think italian importers, etc.)
- gourmet grocer
- two butcher shops and a fresh fish shop
- CVS (yes, they sell groceries! spooky)
- 2-3 bodegas that sell shelf-stable goods, as well as a small collection of fruit and vegetables
If you go expand it to 15 minute bike, the world is truly your oyster, but the primary one that pops up is Trader Joe's.
The most remarkable part of this description, is that it identifies at least 4 or 5 different neighborhoods in NYC, those are only the ones I can think of off the top of my head, and I haven't been close to everywhere.
There's a lot of things to knock about NYC, but it's easily the most walkable city in the US, that I've seen.
I Costco baker told me once that they used less preservative in bread than small bakers. Costco has such a high turnover that they don't need bread that can survive a whole day on the shelf. Same too with their vegetables that spend far less time in transit than they would getting to a tiny farmers market.
Not if that family uses that same truck for commuting every day or for trips to the pharmacy or movie theater or whatever.