A great deal of that activity has taken place in books or short stories or the comic. In game, he's only really left Stormwind three times. Granted, one of those times was the Battle for Undercity, where he and a dashingly handsome draenei warrior carved their way through tunnels full of undead. Still, it's a fair point. If you really want to know Varian, you have to do a lot of homework. Some players play WoW and that's it. If it doesn't happen in game, it doesn't happen. I can relate, as I'm still bummed that Cairne died offscreen, in a book. I wanted to be there to say goodbye to the character, and I still feel a little cheated.
On the flip side, of course, some people ignore things like quest text, flavor text, and cutscenes but will actually sit down and read a leader short story or a book. I know that I've had spirited lore discussions with folks in my guild, yet every time we jump down from the airship onto Deathwing's back, we're escaping out to get to the fighty bits. So having lore in a form disconnected from the gameplay gives those folks a chance to experience it without feeling like they have to choose between them.
So which do you prefer? Do you want it to happen in the game, or are you happy with tie-ins?
World of Warcraft: Cataclysm has destroyed Azeroth as we know it; nothing is the same! In WoW Insider's Guide to Cataclysm, you can find out everything you need to know about WoW's third expansion, from leveling up a new goblin or worgen to breaking news and strategies on endgame play.