But we aren't talking about small towns when we're talking about the urbanist/walkable city/fuckcars crowd though. They actively hate small towns and think that a hyper dense urban center is the only way to achieve their ends. Once again I recommend the dedicated r/fuckcars thread on the Farms here, it's a fun thread and it will go into great detail on the insanity that these people actually believe in.
ETA: They also tend to be deeply anti-social, alcoholics, anti-natalist, and soft on crime.
Humans are, to an extent, still tribal monkeys. We naturally form communities, but they have an upper limit - somewhere around 500 depending on how stressed we are - before they start to fracture.
Move to a small town of 800 in the Midwest (Go Corncobs!), and you'll find that those fuckers on the other side of the railroad/freeway/river are a bit weird. And sure, you can cram all the kids into the same school but you'll find the East Side Massive fighting the West Side Rudeboys, just because.
We (and by "We" I mean sapient humans, not redditors) need territory as well as community, so in an ideal world I should be able to walk from my village, past the fields, and piss on an oak tree to mark it West Side Rudeboys' territory.
Now bear with me, I'm going to apply some math.
If you've done any large-scale gardening (or small-scale farming), you may know that you can feed a family of 4 from 5 acres, in the sort of temperate climate our ancestors worked. Of course, if you organize so that one guy grows beans, one grows beets and one grows pigs in a crop rotation system you can maximize output and free up some time*. If you also want surplus so folk like the doctor, baker, thatcher, priest and blacksmith can just work, you can factor that in as well.
(*My ancestors used that for Morris dancing, but it's not compulsory)
In short, if 400 people dedicate themselves to farming, 100 can be professionals providing other services. I suppose we could be all commie and exclude toddlers and grandma from physical labour (just sit in your rocking chair and open the pea-pods you blind cunt) but that still leaves us 40 "professionals" and I bet one is a Jewish lawyer.
Where was I? Oh yes...
You can feed, clothe, and hire required professionals for a village of 500 people with 2000 acres. That's almost exactly π square miles, or, a circle with a radius of 1 mile. Which takes 15 minutes at a normal walking pace.
That's where it fucking comes from. 15 minutes isn't some magic, arcane number, it's the amount of time it took my grandfather to walk from the field to the pub.
(Also the the amount of time it took to walk from the pub to his house, but 100 yards is a long way at 11pm.)
Redditors don't understand physical community. They don't understand that your neighbors are now "your tribe": They would post a picture of the next door neighbor screaming for help as their house burned down ("Lol boomers, ammirite?") followed by picture of their house burning down ("Why didn't the boomer help me!?") with no intermediate thought. But they do understand 15 minutes.
When people were happy, they stayed within 15 minutes of a community center.
Therefore if we don't let them move beyond 15 minutes of a community center, they will be happy.
Neck yourselves, you fucking retards.