Unitary Advantage Windows: Scale, Schelling Points, and City Size
A simple, wrong model of human settlements is that they have a "tech tree" of amenities. As your population grows, you unlock more of them. Here's an example with made up numbers:
pop 500: 1 elementary school, 1 convenience store
pop 5000: 1 bank, 1 Tim Hortons
pop 50,000: 1 movie theatre, 1 community centre
pop 500,000: 1 good independent record store, 1 local airport that no one uses
pop 5,000,000: 1 fancypants museum with Greek revival architecture and a wing dedicated to large dinosaur skeleton reconstructions, 1 large amusement park complex
As your settlement grows, the tech you unlock at lower populations proliferate. At a medium city of 500k, you might have 80 cafes, 35 elementary schools, 18 grocery stores, and 7 DMVs (the first one of each amenity being "unlocked" at a lower population, and then increasing every so often as the population grows). One interesting thing I've noticed is that there are often benefits of having specifically one of a specific entity, for reasons that rhyme with the concepts of schelling points, natural monopolies, and network effects.
At specific population levels, these benefits, let's call them Unitary Advantages1, outweigh the costs of there only being one of them (generally because the population can really only support one of that amenity anyways at its current size). Then as the population grows it needs more of that kind of amenity, and builds them, and while the net benefit to the population increases from better accessibility, the unique buff of the Unitary Advantage goes away.
Here are some examples I've noticed so far from the city I live in, which has a population of around 700k:
One Centrally Located Soup Kitchen
If all the homeless people in your city go to one place for their daily meals, it creates a Schelling point for all other community services to host pop up services there (nurses, harm reduction workers, ID and housing clinics, social workers, etc), which better connects the homeless with the services they need.
The people working at that soup kitchen also gain an unusually good understanding of the homeless population of the region as a whole and their needs and wants, which is useful for policy work.
Here I'm going to do some perfunctory throat clearing about some downsides of this, but this doesnt particularly excite me to do so the downsides for the other examples will be left as an exercise for the reader.
If the organizers of the soup kitchen are intentionally or unintentionally discriminatory against a subset of the homeless population, that subset is unusually screwed over
Travel has costs, so the fact that there's only one means that homeless people who live on the fringes of the city can't get to it. Plus it pulls the population into a smaller geographical area (which could be good or bad)
The soup kitchen can develop a disproportionate amount of political capital due to dynamics similar to "being the one guy in the friend group with a reasonably nice and centrally located apartment", which is bad if the guys who run it has weird theories about the causes of homelessness or a hidden agenda
One Local Nonprofit Queer Community Organization
It can make sure that there aren't any terrible collisions in ongoing regular events (e.g. scheduling the transgender discussion circle and the queer autistic discussion circle at the same time)
It maintains a supremely good community events calendar. All the other small scale queer event organizers know to submit their events to this one Canonical Calendar which is maintained by paid staff from this one community org. I just assumed that every city will have a singular gay events calendar with like a half dozen listings every day but this doesn't seem to be the case! We're actually unusually lucky to have this. Toronto doesn't have this.
At its regular events, you will get to hear about all of the upcoming special events (community socials, dances, fundraisers etc) through no effort of your own.
So like, in essence, better community cohesion!
One Canonical Community Foundation
Like, say you're a tech company, or a small business owner who just retired, or a generic fancy person. You may get it into your head to put some of your money into an endowment fund for local nonprofits and causes. In my city there's one foundation that you get pointed to for doing this.
This is honestly kind of insane to think about. Whenever there's a new thing happening in the region (e.g. influx of refugees from Ukraine, people deciding that housing affordability is important now) it'll set up a new fund for the cause and this seems to easily get like seven figure amounts redirected towards them. (This is based off of very fuzzy memories and I haven't verified this.)2
Their annual reports are a really really good source of insight on where the local well off people tend to donate to.
NB: most cities in Canada appear to have just one, including big ones like Toronto, Montreal, and Ottawa. Vancouver has a bunch, though, and Winnipeg for some reason has two.
Other Examples I Have Less Commentary About
One online farmer's market service (order your stuff from any number of local farms, pick up everything at the same time at a central location)
One collection at the local library for rare local history books (no need to schlep all over town to different collections; everything's in one room)
One pho place that is hands down the best one
And for ~Fairness, Some Things I Think We Do Kind of Badly
For some reason, the non-underground (so uh, above ground?) art scene here is not great, compared to other cities around here that are a similar size. Our local orchestra just collapsed, and our local museum is not doing so hot and might die at the end of the year.
A fair number of the nicer restaurants in town are all owned by the same handful of restaurant groups and people, so the slightly upscale western dining selection is quite bland.3 Also when the restaurateurs get sloppy we lose like. a double digit percentage of our nice restaurants in the ensuing fallout lmao
Our ONE food critic just packed up and moved to Ottawa. Now there are no food critics.
Anyways, in conclusion the impression I have is that at any population size, some subset of a settlement's amenities will have the unitary advantage buff and will operate unusually well. 700k is not a magical population number or anything, in case it needs to be said. I'm curious what buffs other-sized cities get!
If you know me from ~IRL and you want the local deets type in the name of the region into the password field here all lowercase.