Because, in the interest of full disclosure, I must acknowledge that I too have succumbed to the lure of multiplayer Diablo. And I am no hard-core gamer. First-person shooter games do not inspire me. The last thing I want to do is reenact a World War II dogfight with some Luftwaffe wannabe. But I can't stop playing Diablo, and it's not just because I love hurling fireballs and mowing down Blood Knights.
People do things together.
I saw the truth of this the first time I ran up against the Butcher in a battle.net game. The Butcher is a nasty fellow encountered early on in the Diablo dungeons. He eats weak players for breakfast, and I was unfortunate enough to be annihilated by him several times one evening. In near despair, I asked another player who happened to be in the same game what we could do to get past the Butcher. He suggested a team strategy.