How come every promo series, theres trolls/afkers?

It's getting frustrating, I do well in all my games and as soon as i get to promos I get an afk or a feeder. I've been to my promos 3 times now.

These last recent promo games just annoyed me so much.

I know there's no naming and shaming allowed. So if you want to look up my recent games check out this Yasuo I had in my last game (where I went 9/4/17). HOW DOES A PERSON LIKE THIS GET TO GOLD?! Look at all of his KDA's, I understand KDA isnt everything but come on. An average of 10+ deaths per champ? http://prntscr.com/5xynze Yasuo keeps feeding. Over and over and over.. the team POLITELY asks him to play safer. He just rages on about how he doesn't care and screw this game and screw us he's just on to mess around. I tell him I'm in my promos and ask him if he will actually try so he decides he's going to troll harder. Needless to say we lost. NONE OF US were rude to him to even trigger it, even the other team was asking us in /all if he was a troll.

The second one I was Brand. Destroyed lane, helped the other lanes. Next thing you know our Maokai and Pantheon start arguing about a failed gank and then they refuse to group and act like children. Maokai keeps going in alone because "Pantheon says I'm useless so I'll be useless", he ended up 0/12. Pantheon won't group or act mature, so 3 of us are left to deal with 5 people crushing into our base.

I seriously feel like Riot gives you trolls on purpose just to keep you playing and trying to climb.