I literally have stopped getting them for the past 3 weeks now, just finished 2 games that I won and still didn't get any. I however have no problem getting chests once the reset for them arrives.
The drop rate for key fragments decreases each time you get one, then resets every month. It's to make it easier for less frequent players to acquire a meaningful number of fragments. It narrows the gap between the players that live and breathe League and the ones that just play a single game on Saturday so that everyone can get a shot at Hextech loot.
I'm pretty sure the reset is 30 days from your first fragment drop, rather than the start of the month.
Luck. You have to win though for that chance of key fragment. Your chance increases with premades. Your chance of getting a key fragment also lower each time you get one and reset each month.
its not luck. basically. if you do well and win a game. you will most likely get a key. I don't know the exact time. but you get a chance to get 6 key fragments or so twice a month or 3 weeks. i can tell you that its not a month. its less. 3 weeks at most.
If you queue up in a premade 5, everyone in your premade 5 except you will normally get a key when you win.
Rito: play with friends to increase key drop rate, what you are a solo player? fuck you.
I haven't gotten a key in almost a month now.
In the words of Professor Mcgonagall: "Sheer dumb luck."
