Came in right on Volibear patch. It was funny because my friend (IGN: Vanhour) was badgering me about at least trying League for almost a half a year at this point. I had just finished a barrage of tests (it was my freshman year in college) and admitted I needed a break, so I installed it and started playing.
I actually hated it at first, I had no bloody clue what I was doing. I remember when I couldn't even win against beginner bots, it was humiliating. I got sick of it quickly and went back to WoW for a spell, and then winter break hit and I decimated all of Cataclysm's content and got bored with it. The Pandaria leak did NOT help either, so I decided to not only move to a different game but save a respectable amount of money and try League out again, as I was noticing a lot of people in my dorm were picking it up.
I did some digging, a bit of research (thank you mobafire!) and generally looked closer at the game and just went hogwild. I loved the characters, I thought all the kits were either good or awesome and played as often as I could. With general engineering courses being as they are I had plenty of time on my hands. I swept up several of my friends into LoL as well in my fervor and I quickly developed my reputation for being 'The League of Legends guy'.
So when I think about it, it's simply because I love the game and everything behind it, but me getting started (really started) into LoL was a combination of well-timed conveniences.