Pretty much what Bon said.
Its a fun game, and I play it occasionally for just that reason.
WoW isn't the first MMORPG I've played, (that would be Star Wars Galaxies which was great pre-cu) and I've made a lot of friends from it. Many of these people have met up in meets around Europe. Some of them have gone on to develop romantic relationships. Several I know of have either gotten married or are intending to do so. My wife and I are some of them. And no these are not hideous troglodytes that must hide from society. Most of the girls I known online are very pretty. (And that is especially true regarding my wife)
MMORPG's are just a new way of interacting with people. It also doesn't leave you puking on your shoes and waking up with a hangover like going out to the pub does.
Yes there are some people who spend all their time on MMORPG's but then they are the sort of people who are probably prone to addictive behaviour anyway. You'll also get some more "colourful" characters as well. I've run online roleplays (board based) for about the last 10 years and we've had all manner of people. Mostly normal interesting people, but also a few people with bizarre interests, idea's, or mental peculiarities. Being online can also be an outlet for these people and allows them to come out of their shell more than being face to face.
But more importantly girls like this play