Why are people play this game if they just want to quit?

I've had a nice climb up the ladder form silver to almost Diamond now this past month or 2, and every single game when someone dies they rage for whatever reason and want to quit, even if we are clearly winning? I've seen people rage afk farm because someone took "their" red or blue buff. I've seen people quit because top died twice, or mid fed, or whatever lame reason there is. This is a team game, and one thing I've learned is EVERYONE has bad games sometimes. The difference between games where teams come back and win, and ones where there is a clear loss, is ragers. I don't get why people have to be so sensitive. This is a competitive game. People will die. Instead of talking down to your teammates, try talking them up! Help them when you can. I guarantee you that you will win MANY more games!!!!! Sigh... this is my rant for that overly sensitive group of gamers. Am I the only one that's noticed this?