- For pre-tank times, makes it a lot harder for strangers (e.g. intruding enemies) to get oriented.
- For more modern neighborhoods, make the roads confusing so cars won't take a shortcut through and bypass the main road. (--> keep unnecessary cars out of living areas since they are dangerous to kids on the street and the noise and air pollution is bad)
Alas Waze and its ilk are breaking that system in a lot of European cities. It's now quite common to have quiet residential streets suddenly turn gridlock when some algorithm has correctly-but-malevolently decided it's a good shortcut for everyone getting from the office to the freeway.
When I think of a future powered by AI, I think of that kind of logic casually extinguishing all life on the planet.
There was also the adaptation from cities that were built when walking and horses were the main transportation modes which remain amenable to walking today.
All said, it seems like a renewed interest in the impact of urban design on things like walkability and livability have come back into fashion and some cities are taking their cues from that with their urban renewal projects. As a really interesting example of that has been the evolution of zoning laws which allow for mixed use buildings (commercial and residential) which are sprouting up all around the Bay Area. This is something that was pretty much unthinkable in the late 90's.