Er. Actually, they make their money by having one of the most fascinating gaming systems available. The combat rules suck, okay - but forget all that. If you want to tabletop just blay by GURPS rules, and you're fine. The really important thing about White Wolf's success is the fact that the games are psychologically demanding, meticulously researched (there is definitely bullshit in the history and mythology, but there's also a lot of actual historical fact and religious research - the reason the bullshit is so believable is that it's couched in truth!) and extremely detailed. Vampire, Werewolf, Changeling, all the other games detail subcultures that are so attractive that people not only want to play them, they decide that they want to live them. Which is why you see people referring to new vampires as children or neonates, mentors as sires, experienced members of the community as elders, etc; it's why you see people speaking about blood bonds, coteries, packs, clans...The images of White Wolf have had a very strong influence on popular culture.
Vampire: The Masquerade first came out in 1991. I know. I bought a first edition module when it first came out. (It's been autographed by Andrew Greenberg, whose reaction upon seeing the pristine paperback was "Oh my God, I haven't seen one of those in ages...") When I bought it, I had already played tons of role playing games (AD&D, Elfquest, Space 1889, Runequest, Shadowrun, Night Life, anything else I could find...) I didn't choose Vampire because it was a role playing game. I just saw the word "vampire" on the cover, and the gorgeous red rose on green marble background, and drooled. It was ME! I had to have it! So I bought it (sacrificing a week's worth of groceries, as it was a very slow month and I wasn't making many tips at the bar) and read it in one night. I was entranced. The artwork was beautiful, the mythology was enchanting. And believable. I knew it was a game, but oh, what a beautiful game it was. A game where I could be gothic and a vampire and not have to explain it away because all the other players would be doing the same thing? Hurrah! And furthermore, this was obviously meant for live action, and as much free-form imaginative rule-bending as possible.
That was 1991. Now, years later, White Wolf has caused something of a revolution in the vampire population. Very few vampires are neutral - most vampires seem to love it (dare I say embrace it? The authors did have SUCH a way with language!) or hate it. Role players are either adopted or reviled as poseurs. Personally, I think vampire culture is slowly adapting to make room for the White Wolf elements; there is a lot of friction, but trying to stop the advance of White Wolf is like trying to stop a glacier. The old guard might be aloof, but most of the newer vampires (and oh, have we had a population explosion in recent years) will definitely be touched by the phenomenon, and in the end, the world will have subtly changed.
Will we live in a World of Darkness (TM)? I hope not. However, it's a pretty sure thing that our language, lifestyle habits, dress, and origin theories will be affected for a while. Whether the change will be permanent or not is a tough call. I suspect not. Vampire images in pop culture seem to change based on what society wants to get out of the image of the vampire. What is unusual about White Wolf is that for once, an image of the vampire arose simultaneously with the emergence of a subculture of people who considered themselves vampires and were searching for a raison d'etre, a mode of living, a statement, a creation myth. Synchronicity happened. I think that is what made White Wolf so incredibly powerful. What started as a game with deep spiritual overtones (whether or not one agrees with Christianity, one can see that any game that discusses the possibility of achieving Nirvana, er, Golconda is at least somewhat concerned with the soul as well as the hit points gained on a dungeon crawl) became a lifestyle.
I wish I'd had time to ask Andrew Greenberg what he would think about all this. If I can find his e-mail addy I'll definitely write him.