You're not missing anything; those countries are completely white on the map. "Limited access to streets" is kind of a euphemism for what we used to call "third-world slums" which aren't really a problem in developed countries so those countries probably get a lot less study.

I saw an interesting paper a while back about computing the minimum number of shacks to tear down that would allow putting in new streets/utilities to provide access to every structure. It's a very different mindset from urban planning in the developed world.