Well, that was fun
I don't disagree with your logic. If I were you I might make the same point, and might also disregard my suggestion. And naturally, as I am running it, I am removing those that don't mesh well with our play.
However, understand this:
1) Objectively, so far WotBS has "a lot" of NPCs. Whether used by the DM or not, simply having them adds overhead to the game planning (as well as adding many positive things such as a rich setting and deep and complex environment).
2) when those NPCs carry information or plot hooks, it is not easy to "exclude" them.
Perhaps there is a more happy medium. Perhaps not. I defer that to the authors (and publisher) to decide, but wanted to share my opinion.
The answer, probably, is simply to make it clearer in the text that they're optional. Any of 'em can easily pass on their info and disappear (and even reappear if the DM needs them to).
Perhaps what's lacking is a "DM Advice" sidebar. A short paragraph could solve that easily.