Umm, because it isn't possible? The transition areas between sections are areas that are duplicated on either regions map. As you cross that section, it unloads one map, and loads the other, for hopefully a seamless transition (I've already noticed a few with details missing from one side of the load). And NPCs and objects loaded into one side would have to be unloaded, and reloaded as you passed by. The whole point of these sections is to obfuscate loading, not show it happening. This is why there aren't enemies in map transition areas.