Setting books don't sell. The exceptions are Aztlan and anything about Seattle.
There is also the matter of knowledge and utility. There haven't been a lot of subject matter experts on large swaths of the world. Target: Awakened Lands, aka Target: Australia was written when there were some Aussies in the pool. Shadows of Europe was a fan project that eventually became a thing and was a significant shift in the entire game as a result. Shadows of Asia, however, was not written by a lot of people with deep familiarity with Asia. Now, familiarity in an alternate future setting is a vague thing. Look at Hong Kong in Runner Havens, which I still think is the best location writeup ever done for Shadowrun. Jason Levine is an IRAB (I Read A Book) when it comes to Hong Kong, but he still killed the fuck out of that chapter. North America is something else, similar to Shadows of Europe, but even then you get things like the wildly different material about, say, Chicago between the coverage in Target: UCAS and Feral Cities. Another example is DeeCee. The only real writeup on the sprawl was from 1990, and I had to incorporate that, everything that happened there in the last twenty years (which is actually a lot), my own knowledge of D.C., and the fact that it's a wildly different alternate future from reality. And then there are just areas where I wouldn't trust a whole lot of people with writing about them. Africa is far and away number one on that list.
There is also the matter of utility. One of the reason location books don't sell is because gaming groups tend to keep their games focused in one particular area that they are familiar with, and far and away the one setting everyone who plays Shadowrun knows about is Seattle. If they don't use Seattle, they may use one closer to home, and the amount and usefulness of information tends to be pretty sparse outside of Seattle because it is ten-fifteen years or more between updates to locations in a constantly changing setting. So most people just tend to make up their own material.
The various formats that Catalyst has been using at least has the benefit of putting subject matter books into some measure of perspective by focusing on areas where those subjects are of significance. That's why a lot of tradecraft material in Spy Games and conspiracies in Conspiracy Theories are so present in the material covering Denver, London, and DeeCee. The smaller writeups reflect the fact that if someone uses them, chances are they are going to be temporary, so let's make sure you know who to work for and who to avoid when you're otherwise doing the same thing as in Seattle, but with different accents.
As far as advancing storylines and metaplot goes, it's easier to do in subject matter books and those that focus on global presences like the megacorps and transglobal organized crime. Simple as that.
