DBC Reed has spoken, here:
"Well that's telling you, Frank Lloyd Wright and Fred Pooley: just have big densities in the middle than spread out as you go out a bit."
Why didn't they think of that?
One reason might be different methods of getting about. Some people might want to jump on one of those new-fangled train things and commute for the bearable 40 mins and live 20 miles out in the country. You could call the intervening space, I dunno, a green belt.
If small groups of houses are 20 miles apart, then that is what we would call "spread out" and that is exactly what I said.
The relevant question is, how "spread out" is "spread out" enough to give people the enjoyment/illusion of being surrounded by fields and woodland while keeping the real benefits (convenience, cost, environment) of being not too far from the city center in terms of travel?
I know about this stuff, as I keep my eyes open, and the answer is "Having villages twenty miles apart is fucking ridiculous, of no benefit to anybody and of great harm to nearly everybody.
The combination which gives the highest overall benefit i.e. number of people multiplied by optimum greenery/travel balance is having a 'branches' layout for the whole town. At the outer ends of the branches, you can thin them out a bit, so that each suburb is surrounded with its own little mini-green belt, between a few hundred yards and a mile wide."
Many European cities are laid out like this, whether intentionally or otherwise and it just 'works'. The London commuter suburb I live in now is, coincidentally, exactly like this, it is nearly surrounded by (public) woodland or fields and even though this mini-green belt is in places only a hundred yards wide, it does the trick.
The original post even has diagrams illustrating all this.