Rito cannot effectively determine what the causes of certain cases for inting and afking are so that's where they fall short. Some people can legitimately leave because of real life emergencies and some players just might be having bad games. There are cases in which there is evidence stacking against said players. In times like those you just hope that enough of you report said person(s).
There used to be a tribunal/review process for such games and cases, but as always we can never have nice things because of a few stupid people. Players started to abuse this by just spamming cases without so much as reviewing them in order to receive the rewards given to players who complete them.
Even if Rito were to manually review cases with employees they would have to dedicate a massive team in order to do so. Doing something like so is a big waste of time, money, and resources. Just imagine the hassle that one would go through attempting to review cases.
There are over 1 million+ players in NA alone. Let's just be conservative here and say there are at least 10,000 games played per day in NA. Let's also say that of said 10,000 imaginary games 5% of them result in reports. That's already 500 games/cases that need to be reviewed. Game play would need to be reviewed along side of chat logs. Of course cases would be reviewed multiple times by different people in order to get the most fair results. You can already start to see how massive of an undertaking such a task would become.