What's wrong with the ranked games?

I had just played a ranked game and I am in placements place right now. One of my team mates was afk from the beginning of the game and when we've lost after many surrenders that I have asked and denied, I took a loss. Why is this happened? When I play ranked and have some idiots team mates who wants to stay and loose, I have to take the loss? Because if that's the deal then I should have been afk without any punishment...