Not Getting Hextech Chests

Hi Riot I have been playing for so many days but I've got no chest. I play different characters everyday, had matches where 2 or 3 ppl get s+ and i still dont get a chest. I had one with soraka a month ago and thats it. P.S. You guys maybe should change the point of having free champions. It seems like a waste when the message pops up "You need to have the champion in order to earn its mastery chest" I mean i still get lvls with free champions and get away with it. Just a suggestion. nothing else.