why do i get demoted, lose lp, ect cause i get an afk

i have been on huge tilt, 3 wins in last 13 games, but come on, the game i get demoted in on is a game i get an afk in, how far is that. in my last 13 games ive probably had 6 afks, on both my team and there team, thats really way to many. Thats 6 games ruined of a fair game out of 13 almost 50% fix ur game riot