What actually happens to people who break the summoner's code?

I was at 0 lp for 1 game in Platinum 2, our jungle AFK's at level 6. Sweet, instant demotion and not only was that time entirely wasted, my time will further be wasted by the games I now have to play to climb back to my previous spot. This happens entirely too frequently. This community is so littered by people who ruin games in the variety of ways that are possible. Verbal abuse, trolling, AFKs, etc. The list goes on.

I do not feel like the players fear playing this way. People are not afraid to get banned because the consequences are not scary. I do not understand why going AFK doesn't hurt you. There is just not enough punishment. What happened to loss prevented games? Do those still exist?

I would like to see an AFK in a game and know with certainty that that behavior will not go unnoticed and that person will suffer some time of ban or warning if its only been once.

Take CS:GO's model for example. If someone leaves a match, the game literally tells you immediately what happened to that player. It will tell you how long they are banned for and everything. It's really not complicated.