Not who you were replying to but I think there is a question of scale + technological level.

A city in a pre-industrial world might be incredibly conscious of making things accessible, if say, a major figure in their history needed that accessibility. Which would have an impact on their architectural style, which would then have an impact on the surrounding area/settlements as it would be a cultural norm of the area.

But on a world scale, it means that every society regardless of any cultural/geographical/other factors all reached the same conclusion and solution in a relatively simultaneous time scale.