I have my own campaign world, one I've been working on for over 15 years (started when I was about 12). My world is superficially similar to many other worlds out there, but I am confident that it has enought of its own soul and heart to set it apart and allow it to become popular if given the chance.
That said, I have been being many "crunch" and "fluffy" FR products for about ten years. I bought and continue to buy them for the same reasons I bought Ravenloft, Greyhawk, Planescape, and Tolkein: to make sure that what I'm doing is "original." And, because I like the stories associated with the different settings. Ironically, I don't read the books (the only FR novels I've read are the first three Drow collections, Prince of Lies, and the Avatar Trilogy, all of which I thought to be mediocre to complete garbage respectively), but I like to see the manner in which the stories develop.
Furthermore, I think FR, more than the other settings, reveals just how thoroughly one (or many, as in their case) can create a campaign setting. While I'm sure there are others out there who've done as much, in my observation, the 3ed Forgotten Realms Campaign Setting is probably the most comprehensive example of that kind of book. From currency, timeline, alphabet, trade and merchantism, to stats for key NPCs, rumors for DMs, and Feats and magic items, this was a great presentation. A near perfect meld of "crunch" and "fluff."
I will buy Silver Marches not because I care if WotC goes all crunchy (although, if my campaign proposal is chosen, I may become concerned with this direction); I will buy it because I happen to like reading a mix of both "crunch" and "fluff." Although I'm not interested in copying FR, I am interested in recreating a perfect meld of game play mechanics with role-playing material, and most of the books have provided this. Sure, I have absolutely no use for the Zhentarim Dragon-Flying mages... but I am interested in finding out how to provide statistical information that fits seamlessly with role-playing stuff. Do I fault others for not being interested? Not at all. Purchasing such books for simple purusal is a lot of money spent if you're not interested in the material. Will I be hurt or upset if FR goes all "crunch?" Not at all.
We shall see...