Every so often I'll get involved with (or instigate) a bunch of people playing a game very seriously. I'm going to start with my idea on why I (and other people) do it.
Persistent online games are an opportunity to have a little world where you can have measurable progress toward defined goals. How many bars are you away from the next experience level? What life percentage did you get the Lich King down to before he inevitably devoured your souls for the fourth night in a row?
Real life has no achievements and no progress bars- contemplating the world as a massive game where one could potentially reach the highest levels of accomplishment is a dangerous contemplation. You don't know your class, you don't know your level, and you can't look at any objective metrics of success or completion. Class balance regarding whether the Banker is exploiting unintended player-built game mechanics and the Mystic Practitioner is generally well-tuned but needs more incentives to engage in large-scale multiplayer modes is not a conversation you can have with the developers, and most importantly, you (simulationism aside) can't decide to reroll and try another game mode. We play games because they condense a life experience and let us make long-term memories over short-term time commitments.
Topics, as a species, are hard to stay on. We should probably give up on domesticating them as beasts of burden.
Anyway, to skip ahead a few box cars in the train of thought because I don't feel like writing more analytical paragraphs about why people game, we have a new minecraft server, and I've been playing a lot of it, and as soon as Felix gets nether portals working I'm going to build a horrific arcane tower in the middle of the desert, surrounded in devious traps made of cacti, dynamite, and geographically-anomalous snow golems, which can only be accessed by tunneling through Hell.
It's not World of Warcraft, and it's not League of Legends, and it's what we want right now.