People casually interested in it often use such reference guides (when they are offered for free) to gain additional insight and information into a series they enjoyed.
Also there are MANY people who do *not* buy the books or the merchandise who only had interest in seeing the movies (the tl;dr crowd). Many of them also go to such sites and have been inspired to buy the books based on what they've seen.
There's no question that fan sites like that (and a few others) generated a metric fuckton of cash for Rowling.
Look...I like her books, and I had a chance to read the series before ANYONE was talking about it, because a teacher gave me the first book and asked what I thought of it for their students. It was good, it was REALLY good...but I've also read better. Just off the top of my head, I'd rank 'Number the Stars' waaaay higher on my 'must read' list for kids that age.
It was word of mouth and the fact that kids would sit down and read this shit that got the ball rolling. Even then people thought she was a hack capitalizing off that other writer's "spooky" mystery genre (forget the name offhand but it was goosebumps I think).
Now even as popular as it all was, the movies and licensing catapulted it into the stratosphere. But you don't have any of that shit without the uber fanbois shoveling this shit onto everyone else.
Star Trek is a good analogy. Roddenberry was, quite frankly, a prick to a lot of people. He was very petty. He wrote lyrics to the opening theme music to screw the composer out of half the royalties...that's how much of a dick he was. A lot of people like Star Trek, but it's the uber fanbois that have made it was it is today.
Same with Firefly. Wouldn't be a movie named Serenity without the Browncoat fan base.
Fucking your uber fans is an extremely retarded thing to do. This is an issue which has truly split Rowling's fan community. It would have gone much worse for her I think except the guy she's fucking
has continually defended her even as she's said horrible and nasty things about him personally.
I'm a fucking Harry Potter fanboy, as you'll ALL remember from my lengthy threads discussing her shit.
The last book sucked balls. It was BAD. It was REALLY BAD. And most fans were left feeling more than a little gypped (no slur intended). It came off really half assed and what's terrible...it wasn't.
She just isn't a great writer. Don't get me wrong, she is really fantastic in some ways, and shines...really shines.
But it's like someone on one of those reality talent shows, where they come in and you're just like 'fucking WOW'...but they can't hit the high note.
She can't hit the high note. And I think she knows it.
And she's a one trick pony, there will never be anything else. I'd love to eat those words, I'd love for her to absolutely prove me wrong...but I'm right. This is it for her, and like an aging diva she's going to cling to it tooth and nail, because...that's it.
As to her fan base....only ones who'd BUY the reference guide/encyclopedia ARE the uber fans and the people who really liked the books/movies. And that's who she's shitting on.
Will it cost her? Yep, but people will still buy it. Provided she hurries. Because once the last movie is done...the lights go out and most people will go home.
Even if she's still on stage trying for encores.