Dunno, gaming is now more popular than it was before.
And wow came at the right time; helped by the biggest media campaign ever for a mmorpg.
The paying methods also openned the way to non mmorpg world familiar people (prepaid card,etc).
Edit : no daniel I think you're, in some way, right.
But it's not only child, there are a lot of newbies (who could be adults) as you say.
I've got a big time of /played in wow, and indeed there isn't a lot of substance, a lot of promises were made by blizzard and after months only a few came. And I don't want to wait (and pay) 6 months again to see some good pvp content (that's how it was shown I think, "a pvp game").