So you would much rather have the entire opposing team drop out at about lvl 12 when momentum becomes obvious?
Not drop out, but when the momentum becomes obvious that's exactly when you need quick game enders so that you don't keep the losing team grinding their teeth.
Let's face it, by the time one team has permanent control over the artifact shop and enough gold to afford them, the momentum is obvious and the game needs to end quickly at that point so that the losing team doesn't get pounded for another 20 minutes.
Or how about when you barely get to mid game and are slightly losing to have one of your teammates quit and get replaced with a dumb as fuk computer AI?
This has nothing to do with anything. People will make their own choices when to quit, and this is something you can never control. Some people quit because they die once, doesn't mean there's anything wrong with the game. The best you can do is when it becomes pretty obvious that one team is going to lose, you make that loss come as quickly as possible so the people on the losing team don't have as much reason to drop out.