LP loss due to afk team mate

I wish Riot could do something about losing LP in ranked because of afk team mates. I have lost tons of LP due to people grieving and going afk or even in some cases going afk due to internet issues etc. My question is.... why do I lose LP because I'm forced to play a four vs five because of some other player leaves game for whatever reason? To stop this why doesn't Riot punish the people doing this by demoting them a whole tier? If they are gold three and let's say after three afks they then should just be placed into silver three. I'm not saying demote them for one afk but something must be done. Also maybe consider not making the team who has grieving afk player lose LP but still give to other team because it's not their fault someone went afk. I don't know what else can be done to stop this and it's totally ruining the game for me. If other people have suggestions to fix this problem please leave a comment. I'm just frustrated because people going afk in a game has caused me to lose promos and I even have gotten unlucky and had 3 games in a row where someone went afk. This is a major problem that needs to be addressed. Thank you for your time and I'm looking forward to people's comments and suggestions.