re: Poker & Tournament Raising Strategy?
My impression is that the 2.1 - 2.5x trend comes from the higher stakes games (which then naturally filters down to the adoring hordes at the micro stakes) where play has become ultra-agressive over the last few years with 3-, 4- or even 5-bets becoming common with light holdings.
Players like to raise light, especially from late position, and this is typically correct, since you need to steal blinds to keep your stack growing, particularly as you get deeper into the tourney. As a result, 3 bet ranges have widened up in response.
If you open 3x from the button with 15-20 BB with 30% of your range, and the blinds shove against you plenty, you'll be forced to give up 15-20% of your stack a lot of the time. Raising 2.1x will get you the blinds almost as often, but it's much cheaper to fold if you get shoved on.
That's how I interpret it anyways.