Regional Category Levels

This is my first post here, so I am guessing that this is the proper place to start.
I am puzzled by the regional category levels applied to my hometown, and to civic/neighborhood associations in particular. Most neighborhood associations are listed together, but just a few are one level down, a category named from the particular neighborhood, and then by the association URL. I can provide specifics if desired, but I don't know if that is appropriate.

What may be happening -- what often happens -- is that the subcategories (for specific neighborhood, specific kind of business, specific aspect of society, etc.) do not get generated until they are "needed" -- that is, until there are several sites to go into them.

Might this be the case? Or might this have formerly been the case, but the neighborhoods have now grown enough to warrant their own category?

If the latter, point us to the neighborhood!