I'm sure they gauged high consumer interest for the Handbook series, and that didn't pan out into actual sales. Sometimes a surefire product just doesn't sell well for one reason or another. I'm sure you've probably seen movies, played video games, or read books you thought were absolutely fantastic, but for some reason, they just aren't very popular. You can't win em all. Then there are people who want Product A but flip through it when it comes out, shrug, and then change their mind.
And like I said, it's hard to gauge ACTUAL interest if you only base your opinions on a small and skewed cross section of the fan population (i.e. the online/forum folks). So there'd have to be a way for all of those offline/non-forum fans to have their opinion heard, and that just isn't feasible. Even attending a convention and gauging interest there is still only going to get you the skewed opinion of fans who are dedicated enough to spend time and money on travel, badges, hotels, and such, which is again only a very small percentage of the whole.