I am guessing that you are complaining about people who don't disconnect but stop playing games when losing. You seem to play mostly 30 0 games.
If your opponents disconnect, they have only 5 minutes to reconnect before you are awarded the win. However, if they stay connected, they can just let the time run out.
It is unfortunate. It is possible that they are just lost in thought and let the time run out while they are thinking. That's why chess.com can't automatically forfeit them.
On the other hand, it seems to occur right after a decisive mistake.That is why many people won't play slow chess here.
What to do if there are some asholes who go afk when you beat them, but they haven't lost yeat and have alot of time make their move?